winlogon.exe problem

I'm having a bit of a problem with the winlogon.exe service in windows xp.

I've got all the latest windows updates and service pack so I'm pretty sure MS doesn't know about this problem.

every time i run either 3d Studio Max (R5) or MGI Photovista, the computer slows way the hell down and taskmanager says that winlogon.exe is using about 90% of the cpu. It will continue to be slow with winlogon.exe using all the cpu until I restart the computer.

I've tried terminating the process, but windows says it's a "Critical System Process" and can't be terminated. I've also tried changeing the thread priority. Windows replies with "Access Denied".

The only thing that works (kinda) is to attach a debugger to the process and break execution. It stops winlogon.exe from using all the cpu so i can do whatever in those programs i mentioned.

The only problem is that when i try to restart the winlogon.exe process, my computer resets (as if i hit the reset button).

Anybody know why winlogon.exe is doing this (only with those programs)? Anybody know how to force winlogon.exe's thread priority to BelowNormal (instead of AboveNormal) so that I can use my computer in peace?