I concur with your assumption that some code somewhere "swallowed" the ClassNotFoundException, and just returned an invalid result which then caused this error. Sometimes the server.log file provides more information about such errors. But I always hate it when code does things like this - makes it impossible to debug, as you found out. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4219278#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...