The solution is here https://jira.jboss.org/jira/browse/JBAS-4426 I copy the solution from the link above make sure that you do not have the same library twice. I got the same error, because I had 2 different versions of the same library (jsf-impl.jar): * one in my .war archive under WEB-INF/lib * the other one in jboss-4.2.0.GA\server\default\deploy\jboss-web.deployer\jsf-libs removing the library from my .war archive fixed it I have prove this solution with my problem and I have resolved good luck View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4193003#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...