Could you please take a look at the results of the jboss SerialVersionUIDUnitTestCase: http://cruisecontrol.jboss.com/cc/artifacts/jboss-4.2-testsuite-sun-1.5/2... The component upgrades from 4.0.x to 4.2.x break serialization compatibility in various packages, so I like to review what really needs fixing and what can be excluded: Packages that broke are: javax.fases (myfaces -> sun jsf 2.0 ri) javax.servlet (tomcat 5 -> jboss web 2.0) javax.xml.rpc.soap.SOAPFaultException (?) org.jboss.aspects.versioned.StateManager (kabir) org.jboss.console (?) org.jboss.invocation.iiop.IIOPInvoker$PersistentServantLocator, org.jboss.invocation.iiop.IIOPInvoker$TransientServantLocator, org.jboss.invocation.jrmp.server.JRMPInvoker, org.jboss.invocation.unified.marshall.HTTPInvocationMarshaller, org.jboss.invocation.unified.marshall. org.jboss.proxy.ClientContainerEx, org.jboss.proxy.ejb.DynamicIIOPStub, org.jboss.proxy.ejb.HomeHandleImplIIOP org.jboss.remoting (remoting 2.x) org.jboss.tm.iiop._CoordinatorExtStub, (we can ignore them) org.jboss.tm.iiop._TransactionFactoryExtStub, org.jboss.tm.iiop._TransactionServiceStub, org.jboss.web.tomcat.servlets.ContextForwardServlet, org.jboss.webservice.transport.jms.JMSTransportSupport org.jboss.ws.WSException, org.jboss.ws.metadata..., org.jgroups.*