Thanks Joshua for reply, actually I'm trying to deploy in JBoss 4.2.1 not in 4.05. The problem is that the class SeamApplication12 try to invoke the method addELResolver of com.sun.faces.application.ApplicationImpl, but that method does not exist. I tried to replace the JSF RI by myfaces but I got more problems. So, who is wrong Seam or JSF RI? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4099899#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...