JbossAS 5.0.1 / jbossall-client 4.0.4 backward compatibility

Our old system contained JbossAS4 and several different client applications. As we are building new system, we migrated to Jboss 5.0.1 but we must maintain backward compatibility with old client applications. If we try to connect old application to the new jboss we are recieving

java.lang.ClassCastException: javax.naming.Reference cannot be cast to....

which says how jbossclient-all is not compatible with the AS5 one. If we change jboss client jar with the new libraries, everything works fine but our problem is that we can not change this as applications are in production. I have found following link which is descibing jboss server/client compatibilites, but unfortunatelly I couln't find anything regarding AS5. If you believe what this page is describing, then most of the client/server versions seem to communicate without the problem.

1. Do you guys know if there is a way to make those 2 versions to be compatible?开发者_运维知识库 If there is no way to do it I am having idea of creating "adapter" which will be deployed on jbossASç and will forward the calls to jboss5.

2. Do you have experience making ejb calls within two different jboss versions? It seems how it is not that straightforward. Last option is to use WS calls between jboss4 and 5, but we would like to avoid this, if possible.