I ran into the exact same issue and practically cannot click on anything on the web client. The issue is the conflict with MyFaces in alfresco.war and the JSF implementation jars in jbossweb-deployer. The web.xml context param you specified eliminated this problem with Alfresco 2.0.1 when deployed on JBoss 4.2, but not for Alfresco 2.1.
An earlier post in this forum mentioned to upgrade what is in JBoss to what is in alfresco.war and remove it from alfresco.war. When I tried that it would not even deploy the default apps in JBoss.
Has anyone successfully deployed Alfresco 2.1 on JBoss 4.2? If so, please share your configs.
Thanks.