A call to the getPackageClassLoaders operation of the MBean : JMImplementation:name=Default,service=LoaderRepository throws an exception.

The simpliest way to view the bug :
twiddle invoke "JMImplementation:name=Default,service=LoaderRepository" getPackageClassLoaders javax.ejb.EntityBean

Start of the trace :
java.io.NotSerializableException: org.jboss.mx.loading.ClassLoaderUtils$RepositoryClassLoaderComparator
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1081)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:302)
at java.util.TreeSet.writeObject(TreeSet.java:458)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)

The comparator used by the result TreeSet is not serializable and could not be send to the remote client. (twiddle or a J2EE Client application)

http://viewvc.jboss.org/cgi-bin/viewvc.cgi/jbossas/trunk/jmx/src/main/org/jboss/mx/loading/ClassLoaderUtils.java?view=markup