CVS Checkout of GRUF today :)
Now i've found the problem. I can't quite find the code, but i can now recreate it at least.
1. Make a Plone site
2. Log out
3. Make an emergency user (thats access, not inituser)
4. Restart
5. You can log in to the root ZMI
6. But almost any action on Plone causes the Plone UI to come up, rather than the ZMI.
If you make a normal manager user and log in as that person, bingo its fine. Now I havent been able to spot with a quick look in GRUF where it should be (never looked at it much). However I remember inside the standard acl_users there is special code for finding the emergency user.
This is more of an annoyance that will confuse the hell out of users (like me) than anything serious.