I can remember two last ones in details:
1)While in town trying to move my Blackthorne pants from stash to inventory and the game just froze. I was not doing anything else at the moment
2)While teleporting to town I opened my inventory and tried to remove a white item I picked up. The game froze again.
Both times it happened while I was trying to pickup items, I never got to the point when items were picked up.
I play on windows 7 pro x64. Q6600, HD 3850, 4GB ram.
Both times I was monitoring my CPU and it worked under 80%, I had unsed ram and GPU was not overheating. This started happening around new Year.