JBoss Remoting unmarshalls the entire request before it dispatches the request. A big problem with this is when you are dispatching to a different, non-default, classloader domain in that the parameter classes may not be available during demarshalling and class not found exceptions (or CCE when the dispatch actually gets to the target object) will happen. My bet is that our IIOP layer right now has this problem as well.
The solution would be to not demarshall the method arguments and have invocation.getArguments do a callback to the remoting layer for a demarshall. I don't think this is possible to implement for any IIOP solution or any solution that automatically unmarshalls the buffer.
Maybe I am missing something, but these class loading boundaries are a real flaw in the whole Invoker architecture.