Hi Paul, I will look into this problem shortly. As a matter of fact, I'm pretty sure I'm the one who added the line | setUnMarshaller(unmarshaller); | when I noticed the unmarshaller was getting recreated with each invocation. As my JBoss colleague Aleksandar Kostadinov says, "If it isn't broke, fix it till it is". :-) I've assigned JBREM-900 "ClassCastExceptions when two apps in jboss make concurrent calls to a remote jboss" to release 2.4.0.CR1. -Ron View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4127647#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...