Just to cover all the bases, any overclocking of the graphics card? That's usuallly what causes that particular message to come up for me.

Stop doing it

Seriously, if it's been good for awhile now in other games, that's probably not the issue. But if you want to make sure, return the card to stock clocks, and try playing the game then. If your card is pre-overclocked from the factory, use whatever overclocking program you use to bring the card down to 513Mhz on the core, and 1600Mhz on the memory (iirc).

Well, you've got the latest drivers for your card now, and if the card's been stable elsewhere, nothing else is jumping out at me. Make sure IM isn't set to interrupt you with notifications, I think there have been a few other reports of it screwing with this game.

OT: Overclocking is a bit of a can of worms, and there's a bit of a learning curve if you want to do it safely. Opinions will differ, but one of the best programs out there right is a program called Rivatuner. It's a little complicated to learn at first, but it's reliable and will have no trouble with your card. You can download the program from "http://www.guru3d.com", under their "Downloads" tab. It should be on the "most downloaded" list. This isn't really a hardware forum; your best bet to learn how to use the program (or others) would be to check out a reputable hardware forum where everyone and their pet dog is already doing it. There will almost certainly be stickied "How-to" topics on the issue, where you can get started on reading/learning. Two large, well-established forums of this type are "http://www.hardforum.com/" and "http://www.xtremesystems.com", although there are countless others to be found as well.