Update: It didn't stop crashing, but the game lasts at least 15-30 minutes before doing so. Which is sucky, but at least a lot better than before.
My rig:
Core i7@3,8 GHz (rock stable under prolonged 100% load)
6 GB Memory
ASUS P6T-SE
nVidia GTX 275
I had the same crash problem, within minutes the game started stuttering with heavy hard disk thrashing and then CTD.
I put the -maxmem=2047 on my shortcut and altered the video memory setting to Very high. That seems to have fixed it.