until you do something that requires UAC, or a 3D game. When the UAC
screen dimms, the screen becomes totally scrambled. The same if you
start a 3D game like Doom. There is no clearing the display - the
computer has to be rebooted.

Could it be over-heating in your PC case?

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (Xubuntu 7.04) Linux 2.6.23.12
^ ^ 20:06:01 up 1 day 10:37 0 users load average: 0.25 0.09 0.02
? ? (CSSA):
http://www.swd.gov.hk/tc/index/site_...ub_addressesa/