You also need to change the namespace. It should be:
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
er, of course! When I read that, I thought it meant JBoss5 was looking for the j2ee namespace even though I _thought_ I was using the javaee one.
Thanks for pointing out the obvious.
No problem, the same error bit me when I switched to 2.5.