Hmmm... Not what i expected. Let's try one other approach (again, i am not sure whether its going to pin-point the exact issue. But let's give it a try). Edit the run.bat (if you are using Windows) or run.conf (for Unix) to pass the -verbose:class JVM parameter to the server. run.bat: set JAVA_OPTS=%JAVA_OPTS% -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -verbose:class run.conf: if [ "x$JAVA_OPTS" = "x" ]; then | JAVA_OPTS="-server -Xms128m -Xmx512m -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000" -verbose:class | fi Note: These parameters will have to be all in one line This will print out to STDOUT the classes that are being loaded and the jar files from which they are being picked up. This dump will be huge and remember to redirect STDOUT to some file: run.bat > classes.log Restart JBoss after these changes. Then on, just follow the steps that you normally do, to run into this exception. Once this exception occurs (you will have to keep an watch on either server.log or classes.log to see whether the exception has occured), upload this classes.log to some place where we can access it (you wont be able to post that huge classes log in your post). If we are lucky, then we might figure out what the issue is from these logs. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4126612#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...