Crash/Hanging Usually When Watching Video

Hi all,

I've been having some problems with a computer I built. The spec is in my sig.

Basically, it doesn't BSOD but will sporadically crash and become completely unresponsive (screen freezes, audio stops on last frame to make a buzzing noise, doesn't recover) and I have to restart using the main power button.

This happens most often when watching flash video (like iPlayer or TVcatchup services). It also doesn't seem to like Adobe Audition. It's fairly unpredictable though, sometimes it will run for extended periods without a problem and others will be quite volatile.

I've run a few diagnostic tests. Memtest86 returned no errors having run for 24 hours (19 passes). Prime95 will stop on 3 of the four cours almost instantly, but will continue running on one with both sticks of memory in place. If I take one of the sticks out it will run for maybe 30 mins or so on all four cores then one will drop out, followed by others after - temperatures never go above 50C though.

I've tried a couple of different graphics cards, an ATI HD4650 and the Nvidia 9800gt I'm using now so I think it's unlikely this is the root of the problem.

Thanks for any help you can offer.

edit: oh, and I've checked all my drivers are up to date.

What tests are you running with Prime95?
The Test selection box and the stress.txt file describes what components that the program stresses.

I wonder if a 500 watt PSU is powerful enough.

From your description, I wonder about the channels on your motherboard related to the utilization of dual-channel memory (but not used in single channel).

Have you run MemTest when using both dual-channel and single channel settings?
Have you tested all the sticks individually?
Have you tested all the slots individually?