Authorization schemes don't work without logging into workspace first

Question

Hi,
I've got an application which uses APEX Authentication, but my Authorization Schemes only work if a user logs into the APEX workspace before logging into the application. For example if I've got a tab with its authorization scheme set to Must be Admin user, the tab won't appear unless you log into the workspace first (which end users aren't going to do) and then log into the application. I've pasted an example of one of my authorization schemes below, is it using the wrong function to check the group or something?
Authorization Scheme - Must be Admin user
begin
  if apex_util.current_user_in_group('Admin Users') then
    return true;
  else
    return false;
  end if;
end;Thanks
Edited by: XVar on Apr 13, 2011 2:05 PM

Answer 1

Thanks Vee, I've tried your suggestions but I still can't understand why it's not working.
Here's the authorization setting for my tab (called Super Admin):
http://i62.photobucket.com/albums/h114/XVar/tab_settings.png
The authorization scheme ("SAV Manager - Must be Super Admin"):
http://i62.photobucket.com/albums/h114/XVar/authorization_scheme.png
The results of the PL/SQL region, which uses the same code to detect group membership as the authorization scheme. As you can see this correctly identifies that the current user is a member of the "SAV - Super Admins" group, but the Super Admin tab isn't visible at the top of the page.
http://i62.photobucket.com/albums/h114/XVar/current_groups.png
Obviously the group detection is working fine, but the tab still isn't visible :/ I've got a feeling that I'm being a complete idiot and missing something obvious..