In my first week of play, the game would sometimes freeze up my whole computer. I am using Vista.

That hasn't happened lately, but not almost everytime I quit, the game freezes as soon as I hit the 'quit' button. I am able to still do cntl-alt-delete and then end the game.

It just closed normally a minute ago, so this is not happening every time.

The few times that Arthur has been able to see this on his Vista development system, it's always in low-level Windows video functions, which indicates that it could be related to a video driver issue. This only happens on a small percentage of computers, and even then not every time the game is run. The best advice we can offer is to make sure that your computer's drivers are up to date and that DirectX is functioning properly and reports no errors. The issue does not appear to affect savegame integrity, so it's unlikely to harm your games in progress, even if you're forced to terminate the game from Task Manager. If you're at all concerned about that, you can refer to these procedures to periodically back up your savegame files, just in case they are ever needed.