I have Vista 64 and was experiencing a crash running the demo for more than a few minutes. My guess is a problem in your autosave feature.
I added the following permissions to my "Documents" folder to fix the crash:
Everyone
CREATOR OWNER
Users
It works now.
I have Vista x64 and am having crashes. It seems to happen after the game has been running for a few minutes and often in the middle of conversations.
Fixed by adding permissions to my "Documents" folder:
Everyone
CREATOR OWNER
Users