The game's official boards have been flooded with complaints from users claiming that ATI's 3k, 4k and 5k cards won't run the game in either XP, Vista or Windows 7. In other words, if you bought the game and own an ATI card, you're screwed.
Indeed, things are so bad that online retailer Direct2Drive have placed a notice on their digital shopfront, warning ATI customers of the shortfall. Can't remember the last time I saw something like that happen.
Not the best way for Pandemic to sign off to their fanbase, is it?