Cod waw lock up

I was wondering if you guys could help me out, a few weeks ago I picked up a copy of COD WAW and played through the whole solo campaign just fine, once I finished that I went into multiplayer and gave it a go. Everything worked great for about an hour, then my screen froze and the sound began to stutter, from there I cannot exit the screen in anyway other then resetting the computer. This problem has has repeated itself many times after a random amount of time (generally no less then 20minutes). I have confirmed that it is not the GPU or CPU temperatures, it is not an unstable overclock, and I don't believe it is COD WAW itself as I have tried reinstalling it. So I was wondering if anyone has any guesses as to what might be wrong.

I'm using a core i7 rig with a gtx 275 and windows 7 RC 64-bit and onboard sound (I believe windows 7 is probably the problem but I don't have the slightest clue how to fix it)

also when the game locks up it usually leads to a few seconds of network interruption on the other computers in my house

I would but since it was free windows 7 is the only OS available to me, if theres no other solution ill try and happen into a copy of vista but it seems pointless so close to the windows7 release, its only an annoyance and I'll just live with it if I have to but if anyone has a guess at a solution I'm willing to try it

Any chance the PSU is the problem?

Since it doesn't work on XP, it sounds like a driver/hardware incompatibility problem.

Try:

1. Control Panel > Hardware and Sound > Sound > Speakers > Advanced tab / Set the default format to 24 Bit, 48000 Hz (Studio Quality)
2. Updating audio drivers from mobo manufacturer

I couldn't even play CoD:WaW multiplayer beta until I followed step 1. Search to see if anyone has similar problems with the onboard sound on your motherboard in CoD:WaW multiplayer. If you want to test it on Win 7, make sure to run as administrator and try the compatibility modes.