I have also had this problem in a similar situation.
In tomcat's server.xml file I defined a context /develop that points to my htm/jsp development and in my ear I have / as the only context. When I first start JBoss both are ok. As soon as I re-deploy the ear, the /develop context from server.xml disappears? I don't know why this happens but it is frustrating since it means that I need to re-ear and re-deploy every time I alter a jsp during the development cycle. If you have found a solution, please post. Thanks.