EJBException with "Invalid invocation, check your deployment packaging..." msg

An exception like the following:

javax.ejb.EJBException: Invalid invocation, check your deployment packaging, method=public abstract SomeInterface SomeClass

indicates that there is an inconsistent type system between the caller of the ejb and the ejb container. This is due to the caller and ejb container using two different class loaders to load a class involved in the ejb call using a call by reference semantic (which might be true even when using remote interfaces if CallByValue is set to false in ear-deployer.xml). See the JBossClassLoadingUseCases page for details on class loader configuration and packaging issues.