Strange PC Computer Problem - Screen Goes blank

[True North]

I am getting a very odd computer crash on my computer.

Basically, my screen goes blank after 15 minutes to an hour after turning it on. It seems to be aggravated (i.e. happens quicker) when I am in Cubase.

I thought it might be the video card, but I noticed that when I was recording, after the screen goes blank, the sound sort of cackles out - so that led me to beleive that it might be linked to my sound cards (Lynx AES16's)

When I am not using Cubase I can get about an hours worth of work done before "lights out". When using cubase it goes down at about 30 minutes the first and then every 15 minutes after rebooting.

The computer doesen't shut itself off. I have to hold down the power button to shut the computer down.

Anyone ever have this happen to them?

Any suggestions?

Cheer!