Just a little info from my side.
I have the same problem. except....I can play for various times before I freeze(2 minutes - couple of hours).
I cirvumvented the problem by placing a large fan infront of the open case. My problem seems to be an over heating issue.
It tends to be worse when the room my comp is in gets over 75-80 degrees.
I first noticed it when I upgraded video cards.
I have an AMD 1800+ with 4x AGP. The video card is an 8x AGP. Not sure if that is the cause of the problem or not.
I plan on upgrading the motherboard and CPU as well as getting a better case with efficient cooling. I hope that solves the problem.
Don't know if you are having a similar issue, but you may try the fan solution, see if it allows you to play any longer. If it does, you should upgrade/fix the cooling on your current case.
-Derrek