3
Not sure if you've fixed this, but I also had the problem, it seemed to have been caused by the permissions on the cache folder had been changed??
and also, when I looked in the cache folder the adminmenu.php file had vanished, I chmod'd the permissions and dumped a copy of the adminmenu.php in the folder, and that seemed to have solved it!
hope this helps (if you not fixed it already)
Dave