what happens ?
is it because the name changes so the portlet references are changed ? if so you can have a file jboss-app.xml in WEB-INF and the portal will use it to namespace your portlets instead of using the war file name:
<jboss-app> <app-name>portal</app-name> </jboss-app>
What happens is the new portlets (after renaming) are not deployed again (or atleast not rendered on the page). I am surprised just renaming a war can have such an effect. ( I could be doing something wrong though ..)
I will have to try the jboss-app.xml approach you have suggested.
JBoss AS names the context of your web application based on the name of the war file as default. If you change the name you change the context, unless you specify it in jboss-web.xml.
The other option is to use Julien's solution.