"jaikiran" wrote : See if this version matrix helps http://www.jboss.org/community/docs/DOC-10808 That does help indeed. I now realize I misunderstood the situation: it's not that versions -always- need to match exactly, but there are compatibility ranges. I did notice though that the 2 incompatibilities I found (Jboss 4.2.2 client with Jboss 4.2.3 server, and Jboss 4.2.3 client with Jboss 5 server), are not listed in the matrix. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4200112#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...