The high-level answer is that your client and the server need to be using the same versions of the classes that are being serialized and transferred. To do this, you need to package the jboss422/lib/jboss-common.jar into your application. You will have to set up a loader repository so that you app will use this jar file instead of the one that comes with jboss325. That is the general idea. Whether it will work in practice, I don't know because I have not tried it. Also, not having tried it, I could not provide any details on getting it to work. Loader repository (class scoping) ref: http://www.jboss.org/community/docs/DOC-9288 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4187491#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...