Constant crashing but only when playing mods.

So, I've come across something very annoying. Whenever I play a mod, I will often crash almost every turn, or at least within 20 minutes. The graphics freeze but the sound still plays. This can occur when troops are moving, when other factions are taking their turns, when I'm getting pop-up boxes, etc (but haven't had it happen in a battle so it must be something with the campaign map). I can't CTR-ALT-DEL and I have to manually turn off the computer.

When I play regular campaign games, it's fine, but I've tried VanillaMod, LTC and one other and the same reason. I was actually about to play LTC for about four hours, then it started happening again. Very frustrating. I've searched and found someone with a similar problem in past posts but no one seemed able to help him. I have a GeForce 7600 and I've tried it with new and older drivers. I also have Steam and have tried it both unpacked and packed. It doesn't seem to be happening in my other games (BF2, Counter-Strike, Civ4, Company of Heroes).

I've done a fresh install and still had these problems. I've tried using the lowest graphics settings, different shader versions, going from two cores to one in my BIOS and probably a few other things I'm forgetting.

Any ideas?