I have also started experiencing crashes, on CMBN. I had always regarded these games as extremely stable, so it was a surprise. One possible clue - each time it was when I went AFK for about 20-30 minutes. Since then, I have not gone AFK and left the game running, and it hasn't happened again so far. I wonder if a Windows update is causing the problem. Nothing has changed on my rig. Except maybe an Nvidia driver update some time ago.