Did you get anywhere with this, ie JBoss 4.0.3 talking to 4.2.2? We facing the same situation and were also wondering what 'you must use the legacy rmi invokers' means... According to the compatibility matrix, 4.0.4 can talk to 4.2.2 with a compatibility mode flag, and we're assuming 4.0.3SP1 can talk to 4.0.4, since that interaction is not specifically spelled out. So we're thinking about moving legacy apps to 4.0.4 to help creep out of this backwards compatibility hole JBoss has dug for us... Also assuming moving from 4.0.3SP1 to 4.0.4 is relatively trivial. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4159048#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...