We already know that game developers tweak code to perform better on ATI and Nvidia cards, which means the game developer is providing code customized to the card. So, if the developer is handling the memory directly on the card, then there is room for this sort of error that could cause irreconcilable memory hadling issues.
Or...it might be some kind of memory leak. Is 1600x1200 the max for the card? It would be interesting to chart crash frequency to resolution.
---Hog. Gore Hog.