GenericSignatureFormatError with GAE 1.7.5

I tried to upgrade from Weld 1.2.0.Beta1 to 2.0.0.Beta 3, and Hibernate Validator from 5.0.0.Alpha2 to 5.0.0.Beta 1.

Now I'm getting a ResourceLoadingException caused by a GenericSignatureFormatError. Please see the log fragment and the stacktrace below.

Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.descriptor.ReturnValueDescriptorImpl because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.raw.ExecutableElement$MethodElement because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.descriptor.ParameterDescriptorImpl because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.descriptor.ExecutableDescriptorImpl because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.raw.ExecutableElement$SimpleMethodFilter because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.descriptor.PropertyDescriptorImpl because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.descriptor.BeanDescriptorImpl because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.raw.ExecutableElement because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.raw.ExecutableElement$ConstructorElement because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.metadata.descriptor.ElementDescriptorImpl because of underlying class loading error
Feb 24, 2013 12:32:47 PM org.jboss.weld.bootstrap.BeanDeployer addClass
INFO: WELD-000119 Not generating any bean definitions from org.hibernate.validator.internal.engine.ValidatorImpl because of underlying class loading error
Feb 24, 2013 12:32:48 PM org.jboss.weld.environment.servlet.Listener contextInitialized
INFO: No supported servlet container detected, CDI injection will NOT be available in Servlets, Filters or Listeners
Feb 24, 2013 12:32:49 PM org.jboss.weld.interceptor.util.InterceptionTypeRegistry <clinit>
WARNING: Class 'javax.ejb.PostActivate' not found, interception based on it is not enabled
Feb 24, 2013 12:32:49 PM org.jboss.weld.interceptor.util.InterceptionTypeRegistry <clinit>
WARNING: Class 'javax.ejb.PrePassivate' not found, interception based on it is not enabled
Feb 24, 2013 12:32:49 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: Failed startup of context com.google.appengine.tools.development.DevAppEngineWebAppContext@12dba93

{/,C:\Software\eclipse-workspace-gae\shop\war}

org.jboss.weld.resources.spi.ResourceLoadingException: Error loading class de.shop.artikelverwaltung.service.ArtikelObserver$Proxy$_$$_WeldSubclass
at org.jboss.weld.resources.ClassTransformer.getBackedAnnotatedType(ClassTransformer.java:166)
at org.jboss.weld.resources.ClassTransformer.getBackedAnnotatedType(ClassTransformer.java:177)
at org.jboss.weld.resources.ClassTransformer.getEnhancedAnnotatedType(ClassTransformer.java:206)
at org.jboss.weld.injection.producer.SubclassedComponentInstantiator.initEnhancedSubclass(SubclassedComponentInstantiator.java:63)
at org.jboss.weld.injection.producer.SubclassedComponentInstantiator.<init>(SubclassedComponentInstantiator.java:57)
at org.jboss.weld.injection.producer.SubclassedComponentInstantiator.<init>(SubclassedComponentInstantiator.java:53)
at org.jboss.weld.injection.producer.DefaultInjectionTarget.initializeAfterBeanDiscovery(DefaultInjectionTarget.java:108)
at org.jboss.weld.injection.producer.InjectionTargetInitializationContext.initialize(InjectionTargetInitializationContext.java:42)
at org.jboss.weld.injection.producer.InjectionTargetService.initialize(InjectionTargetService.java:57)
at org.jboss.weld.bootstrap.WeldBootstrap.deployBeans(WeldBootstrap.java:470)
at org.jboss.weld.environment.servlet.Listener.contextInitialized(Listener.java:173)
at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:548)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:136)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
at org.mortbay.jetty.Server.doStart(Server.java:224)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:228)
at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:255)
at com.google.appengine.tools.development.AbstractServer.startup(AbstractServer.java:79)
at com.google.appengine.tools.development.DevAppServerImpl$Servers.startup(DevAppServerImpl.java:451)
at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:198)
at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:333)
at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48)
at com.google.appengine.tools.development.DevAppServerMain.<init>(DevAppServerMain.java:269)
at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:245)
Caused by: java.lang.reflect.GenericSignatureFormatError
at sun.reflect.generics.parser.SignatureParser.error(SignatureParser.java:126)
at sun.reflect.generics.parser.SignatureParser.parseFieldTypeSignature(SignatureParser.java:299)
at sun.reflect.generics.parser.SignatureParser.parseFieldTypeSignature(SignatureParser.java:285)
at sun.reflect.generics.parser.SignatureParser.parseTypeSignature(SignatureParser.java:487)
at sun.reflect.generics.parser.SignatureParser.parseTypeSig(SignatureParser.java:190)
at sun.reflect.annotation.AnnotationParser.parseSig(AnnotationParser.java:387)
at sun.reflect.annotation.AnnotationParser.parseAnnotation(AnnotationParser.java:200)
at sun.reflect.annotation.AnnotationParser.parseParameterAnnotations2(AnnotationParser.java:152)
at sun.reflect.annotation.AnnotationParser.parseParameterAnnotations(AnnotationParser.java:129)
at java.lang.reflect.Method.getParameterAnnotations(Method.java:757)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedMethod.initParameters(BackedAnnotatedMethod.java:48)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedMethod.initParameters(BackedAnnotatedMethod.java:27)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedCallable.<init>(BackedAnnotatedCallable.java:34)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedMethod.<init>(BackedAnnotatedMethod.java:38)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedMethod.of(BackedAnnotatedMethod.java:32)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType$BackedAnnotatedMethods.computeValue(BackedAnnotatedType.java:190)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType$BackedAnnotatedMethods.computeValue(BackedAnnotatedType.java:183)
at org.jboss.weld.util.LazyValueHolder.get(LazyValueHolder.java:35)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType$EagerlyInitializedLazyValueHolder.<init>(BackedAnnotatedType.java:151)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType$BackedAnnotatedMethods.<init>(BackedAnnotatedType.java:183)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType$BackedAnnotatedMethods.<init>(BackedAnnotatedType.java:183)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType.<init>(BackedAnnotatedType.java:63)
at org.jboss.weld.annotated.slim.backed.BackedAnnotatedType.of(BackedAnnotatedType.java:44)
at org.jboss.weld.resources.ClassTransformer$TransformClassToBackedAnnotatedType.apply(ClassTransformer.java:78)
at org.jboss.weld.resources.ClassTransformer$TransformClassToBackedAnnotatedType.apply(ClassTransformer.java:75)
at com.google.common.collect.ComputingConcurrentHashMap$ComputingValueReference.compute(ComputingConcurrentHashMap.java:355)
at com.google.common.collect.ComputingConcurrentHashMap$ComputingSegment.compute(ComputingConcurrentHashMap.java:184)
at com.google.common.collect.ComputingConcurrentHashMap$ComputingSegment.getOrCompute(ComputingConcurrentHashMap.java:153)
at com.google.common.collect.ComputingConcurrentHashMap.getOrCompute(ComputingConcurrentHashMap.java:69)
at com.google.common.collect.ComputingConcurrentHashMap$ComputingMapAdapter.get(ComputingConcurrentHashMap.java:393)
at org.jboss.weld.resources.ClassTransformer.getBackedAnnotatedType(ClassTransformer.java:162)
... 30 more