Note, this occurs even though I have jboss-aop-client.jar, which contains org.jboss.aop.instrument.Untransformable, in my client's classpath. Here's the stack trace:

2009-05-27 07:54:31,035 WARN [InventoryManager.discovery-1] (rhq.core.pc.inventory.InventoryManager)- Failure during discovery for [Embedded Web Application Context] Resources - failed after 250 ms.
java.lang.Exception: Discovery component invocation failed.
at org.rhq.core.pc.util.DiscoveryComponentProxyFactory$ComponentInvocationThread.call(DiscoveryComponentProxyFactory.java:248)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.IllegalStateException: org.jboss.remoting.InvocationFailureException: Unable to perform invocation; nested exception is:
java.lang.RuntimeException: javassist.CannotCompileException: by java.lang.NoClassDefFoundError: org/jboss/aop/instrument/Untransformable
at org.rhq.plugins.jbossas5.util.ManagedComponentUtils.getManagedComponents(ManagedComponentUtils.java:160)
at org.rhq.plugins.jbossas5.util.ManagedComponentUtils.getManagedComponents(ManagedComponentUtils.java:141)
at org.rhq.plugins.jbossas5.WebApplicationContextDiscoveryComponent.getWebApplicationComponents(WebApplicationContextDiscoveryComponent.java:182)
at org.rhq.plugins.jbossas5.WebApplicationContextDiscoveryComponent.discoverResources(WebApplicationContextDiscoveryComponent.java:90)
at sun.reflect.GeneratedMethodAccessor67.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.rhq.core.pc.util.DiscoveryComponentProxyFactory$ComponentInvocationThread.call(DiscoveryComponentProxyFactory.java:244)
... 5 more
Caused by: org.jboss.remoting.InvocationFailureException: Unable to perform invocation; nested exception is:
java.lang.RuntimeException: javassist.CannotCompileException: by java.lang.NoClassDefFoundError: org/jboss/aop/instrument/Untransformable
at org.jboss.remoting.transport.socket.SocketClientInvoker.handleException(SocketClientInvoker.java:142)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.transport(MicroSocketClientInvoker.java:891)
at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:165)
at org.jboss.remoting.Client.invoke(Client.java:1724)
at org.jboss.remoting.Client.invoke(Client.java:629)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:60)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
at org.jboss.aspects.remoting.MergeMetaDataInterceptor.invoke(MergeMetaDataInterceptor.java:74)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
at org.jboss.aspects.security.SecurityClientInterceptor.invoke(SecurityClientInterceptor.java:65)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
at org.jboss.aop.generatedproxies.AOPProxy$1.getComponentsForType(AOPProxy$1.java)
at org.rhq.plugins.jbossas5.util.ManagedComponentUtils.getManagedComponents(ManagedComponentUtils.java:156)
... 12 more
Caused by: java.lang.RuntimeException: javassist.CannotCompileException: by java.lang.NoClassDefFoundError: org/jboss/aop/instrument/Untransformable
at org.jboss.aop.proxy.MarshalledInterfaceProxy.readResolve(MarshalledInterfaceProxy.java:76)
at sun.reflect.GeneratedMethodAccessor973.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeReadResolve(ObjectStreamClass.java:1061)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1762)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at java.util.HashMap.readObject(HashMap.java:1030)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at java.util.HashSet.readObject(HashSet.java:291)
at sun.reflect.GeneratedMethodAccessor30.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at org.jboss.aop.joinpoint.InvocationResponse.readExternal(InvocationResponse.java:119)
at java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1792)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1751)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at org.jboss.remoting.serialization.impl.java.JavaSerializationManager.receiveObjectVersion2_2(JavaSerializationManager.java:238)
at org.jboss.remoting.serialization.impl.java.JavaSerializationManager.receiveObject(JavaSerializationManager.java:138)
at org.jboss.remoting.marshal.serializable.SerializableUnMarshaller.read(SerializableUnMarshaller.java:123)
at org.jboss.invocation.unified.marshall.InvocationUnMarshaller.read(InvocationUnMarshaller.java:59)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.versionedRead(MicroSocketClientInvoker.java:1220)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.transport(MicroSocketClientInvoker.java:850)
at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:165)
at org.jboss.remoting.Client.invoke(Client.java:1724)
at org.jboss.remoting.Client.invoke(Client.java:629)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:60)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
at org.jboss.aspects.remoting.MergeMetaDataInterceptor.invoke(MergeMetaDataInterceptor.java:74)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
at org.jboss.aspects.security.SecurityClientInterceptor.invoke(SecurityClientInterceptor.java:65)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
at org.jboss.aop.generatedproxies.AOPProxy$1.getComponentsForType(AOPProxy$1.java)
at org.rhq.plugins.jbossas5.util.ManagedComponentUtils.getManagedComponents(ManagedComponentUtils.java:156)
at org.rhq.plugins.jbossas5.util.ManagedComponentUtils.getManagedComponents(ManagedComponentUtils.java:141)
at org.rhq.plugins.jbossas5.WebApplicationContextDiscoveryComponent.getWebApplicationComponents(WebApplicationContextDiscoveryComponent.java:182)
at org.rhq.plugins.jbossas5.WebApplicationContextDiscoveryComponent.discoverResources(WebApplicationContextDiscoveryComponent.java:90)
at sun.reflect.GeneratedMethodAccessor67.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.rhq.core.pc.util.DiscoveryComponentProxyFactory$ComponentInvocationThread.call(DiscoveryComponentProxyFactory.java:244)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:72)
... 19 more
Caused by: javassist.CannotCompileException: by java.lang.NoClassDefFoundError: org/jboss/aop/instrument/Untransformable
at javassist.ClassPool.toClass(ClassPool.java:1035)
at javassist.scopedpool.ScopedClassPool.toClass(ScopedClassPool.java:306)
at javassist.CtClass.toClass(CtClass.java:1094)
at org.jboss.aop.instrument.TransformerCommon$ToClassAction$2.toClass(TransformerCommon.java:331)
at org.jboss.aop.instrument.TransformerCommon.toClass(TransformerCommon.java:139)
at org.jboss.aop.proxy.ProxyFactory.createProxyClass(ProxyFactory.java:126)
at org.jboss.aop.proxy.ProxyFactory.createInterfaceProxy(ProxyFactory.java:96)
at org.jboss.aop.proxy.MarshalledInterfaceProxy.readResolve(MarshalledInterfaceProxy.java:72)
at sun.reflect.GeneratedMethodAccessor973.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeReadResolve(ObjectStreamClass.java:1061)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1762)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at java.util.HashMap.readObject(HashMap.java:1030)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at java.util.HashSet.readObject(HashSet.java:291)
at sun.reflect.GeneratedMethodAccessor30.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at org.jboss.aop.joinpoint.InvocationResponse.readExternal(InvocationResponse.java:119)
at java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1792)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1751)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at org.jboss.remoting.serialization.impl.java.JavaSerializationManager.receiveObjectVersion2_2(JavaSerializationManager.java:238)
at org.jboss.remoting.serialization.impl.java.JavaSerializationManager.receiveObject(JavaSerializationManager.java:138)
at org.jboss.remoting.marshal.serializable.SerializableUnMarshaller.read(SerializableUnMarshaller.java:123)
at org.jboss.invocation.unified.marshall.InvocationUnMarshaller.read(InvocationUnMarshaller.java:59)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.versionedRead(MicroSocketClientInvoker.java:1220)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.transport(MicroSocketClientInvoker.java:850)
at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:165)
at org.jboss.remoting.Client.invoke(Client.java:1724)
at org.jboss.remoting.Client.invoke(Client.java:629)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:60)
... 19 more
Caused by: java.lang.NoClassDefFoundError: org/jboss/aop/instrument/Untransformable
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
at sun.reflect.GeneratedMethodAccessor974.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javassist.ClassPool.toClass2(ClassPool.java:1047)
at javassist.ClassPool.toClass(ClassPool.java:1029)
... 82 more
Caused by: java.lang.ClassNotFoundException: org.jboss.aop.instrument.Untransformable
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 89 more