I tried to reproduce this issue. The error only affects the application which ships the xercesImpl.jar (or other xerces/xml related jars). Although the 3 log lines that you posted might give an impression that its affects other (default) apps too, but in reality it just fails to deploy only your application. The fix is to isolate your deployments with classloader isolation configuration http://www.jboss.org/community/wiki/ClassLoadingConfiguration Also see this http://www.jboss.org/index.html?module=bb&op=viewtopic&t=154592#4... If none of it works, feel free to post more details (including what those changes lead to). View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4246378#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...