You need to use a different classloader.
Only the management portlet is using JSF (and we will get rid of that dependancy). So you could move the MyFaces libraries from server/default/deploy/jbossweb*/jsf-libs to bundle them with the management portlet and use the Sun RI libs to bundle them in your war.
Please then give us feedback on how it worked, i never tried ICEfaces in a portlet environment.
Ok. Thanks will try and then aswer.