A couple of questions, if I may. Have you waited awhile to see if the OS is possibly doing any "churning" and might finish rendering your screen? For example, every once in awhile my XP, upon reboot, will take a couple of minutes doing "something" with the swap file - I can't imagine what. The only way I know this is that my swap file is on a third hard drive and I can see the drive light flashing. Anyway, when this happens, can you get to the Start Menu (or anything) with a click or Ctrl-Esc, or is everything including your mouse, locked up?
<hr>...If I put the user away from the adiministrator-group, everything works fine... <hr>Does this mean you changed the user to a "limited" user or that you logged on as another user? In either case, I don't know of a fix (yet) and you might just have to create a new user profile. But let's wait to see if anyone else chimes in. It's Christmas morning and (almost) everyone but you and I is away from The Lounge right now. Hang in there a bit, OK?