Exception java.lang.ClassCastException: com.sun.faces.config.WebConfiguration cannot be cast to com.sun.faces.config.WebConfiguration while deploying EAR in JBOSS AS.

If you get the exception mentioned above while you try to deploy your EAR file on the JBoss Application Server, it might help to remove the jsf-impl.jar from the WAR file, which is located within the EAR file. It seems that the AS brings his own implemention with it and that results in the exception.

See also http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4111650#4111650.