Hello,
I tried to get the UserModule from the portlet by using :
UserModule um = (UserModule)getPortletContext().getAttribute("UserModule");
In portal 2.4 modules (ant other services) injected into portlet using
jboss-portlet.xml descriptor.
Take a look at it in core/src/resources/portal-core-war/WEB-INF
make sure you've deployed your portlets with appropriate services injected.