If i remember correctly, the Seam Plugin is said to work under Netbeans 5.5 with Seam 1.2.1 GA which works on JBoss 4.0.5 (JEMS Installer with ejb3 profile). I think you are using incompatible versions. With JBoss 4.2, they threw out Myfaces to put the Sun reference implementation in there instead. Re-adding the jar files in the lib folder wont be enough, I think. So, basically, figure out the correct versions and consider not using Netbeans 6 right now. I have used the latest build today and it threw exceptions while editing a regular facelet file. That IDE is awesome, but not production ready let alone near a beta status. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4080631#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...