A note: If you've upgraded JBoss 4.0.4-GA to EJB3 using the patch installer, the EJB3 libs in $JBOSS_HOME/client are not updated. If you continue to use these libs when accessing EJB3s from an RC9 server, you'll get something similar to this on deserialization: Root exception is java.io.InvalidClassException: org.jboss.ejb3.remoting.IsLocalInterceptor; | local class incompatible: stream classdesc serialVersionUID = -3758782076801249473, local class serialVersionUID = 595045557897063404] ...because the EJB3 Proxy doesn't declare a serialVersionUID, as noted in http://jira.jboss.com/jira/browse/EJBTHREE-402 So use the JARs in $JBOSS_HOME/server/{instanceName}/deploy/ejb3.deployer. Hoping this will save someone out there some time. S, ALR View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3974958#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...