Solutions to errors » I need help – my monitor turns itself off (or graphics card malfunctioning?)?

Firstly, let it be said that this occurs mostly when I play World of Warcraft (I know I’m a junkie ). What usually happens is that the screen freezes for anywhere up to 5 minutes, during this time I can move my mouse freely, but cannot alt+tab, alt+F4, ctrl+alt+del or anything else. After the 5 minutes of a frozen screen my monitor goes black and I have to manually restart my computer.
It happened only once that after the frozen screen I got an error message from windows saying: “The nv4_disp display has stopped working normally. Save your work and reboot the system to restore full display functionality. …”

I have ruled out overheating issues, because I’m currently working with my PC-case’s sidepanel removed, shouldn’t be able to overheat like that.
With some technical advice from the WoW forums, I downloaded a program called nTune (a device for checking up on NVIDIA hardware) and I ran a “stability test”, which is supposed to last 10 minutes – and I got the same kind of crash as I get in the game after about only 3 minutes. And I can’t see what the problem is (obviously) since I only have a black screen to look at.

This is really, really, immensely, and I repeat, really frustrating, any help/ideas/suggestions on this would be oh so much appreciated!
It can’t be anything too obvious, since my PC came back from a repairman just a week ago, and if he missed it, it must be something pretty subtle…
[quote]Did you reboot your PC?[/quote]
Rebooted my PC like 15 times today because of it. So… yes.
It’s not a rare occurrence and I’m getting the feeling I should stop playing until this is resolved, because frequent forced reboots can’t be healthy.