It looks like you're using Boot Camp? Others have experienced issues with it before.
When you checked ATI's site, did you try the desktop drivers or the mobility drivers?
You may also try checking the 'throttle frame rate' option in game. It's possible that the laptop is overheating (yes, even if more 'intense' games don't, GC2 can).
I've tried both mobility, and desktop versions of the drivers, and neither complete installation, they both start installing, and then freak out about 30 seconds later to tell me the card I have is not compatible. Meanwhile Mac offers no new drivers. I think its mostly because apple has the wonderful habit of not supporting its "older" hardware, even if your hardware is literally less then a year old. As long as they have a "newer" model out, your screwed.
I tried the throttle frame rate option as well, and it hard restarted faster then ever before, I got maybe 10 minutes before the crash. And its not overheating. With bioshock after about 2 hours the casing itself got hot enough that while it wasn't painful to touch, it was a little worrying. Galciv2 barely registers a heat increase.
I've changed up pretty much all of the settings, AA, shadows, etc. Nothing seems to work, and no single option, or grouping of options seems to have an average time increase before the hard restart. I did manage to get nearly a half hour out of it about 2 nights ago. But sadly thats about just about enough time to build 1 custom ship in the shipyard, and then hit end turn.
This is getting pretty sad :/ I'd love to be able to play this game.
