[xwiki-users] Container authentication

I'm wanting to use container (tomcat) authentication with XWiki so that I can use a single sign on solution, using the instructions found here: http://platform.xwiki.org/xwiki/bin/view/AdminGuide/Authentication#HContain… I managed to get something basic set up and the authentication is working (the container challenges me for username/password) but when the XWiki page displays it is completely unstyled (though I see my username in the content so the authentication is being picked up) and it displays an "Error. You are not allowed to view this document or perform this action" error message in the page. So its looking like XWiki is not picking up (or generating) some resources it needs for that authenticated user (presumably because it did not go through the user registration process). Or is it expected some specific role to be assigned to the user? What's the trick to get this working correctly? And on a related topic, is there a way to get XWiki to understand additional user credentials such as their real name e.g. from the authentication token or whatever? Thanks Tim