I can successfully deploy this .war file in JBoss 4.0.x, but not in JBoss 4.2.0
I believe it could be a conflict between built-in JBoss JSF/ADF support and the libraries being included in the .war file.
I am currently "mucking" about with the .war file trying to remove libraries and I am getting the application to deploy error-free... but when I try to access a jsp page, I get the same error at that time instead. So not much progress thus far.
JBoss 4.0.x and 4.2.x are packaged with different implementations of JSF. I've the same problem than you, and I found the solution at http://wiki.jboss.org/wiki/Wiki.jsp?page=JBoss5AndMyFaces.