Well, I've just gotten back from a few hours playing crash free. I'm not even going to pretend to understand why MMM repeatedly reduced crash frequency, but I think my issue is solved, and I've learned an important lesson: Leave things alone!

Performance is also now much more in line with what I expected (As in: flawless). Again I'm not going to pretend to understand how this would reduce performance but keep framerate totally stable, but there you go.

How did you turn it off, I'm wondering if AO is on on my GFC and this might fix my game as well! Just wondering how you did this again, because I guarantee you'll find at least five threads of mine related to CTD...

Right clicked on my desktop, clicked on nVidia Control Panel, manage 3D settings, and Ambient Occlusion is the first one. There are also lots of other fancy options for forcing things like AA and AF.
You can also specify these per-application, which is probably a better idea for anybody wanting to force things. (The AO isn't that great, I'd been noticing it for a while because of how badly it interacted sometimes, but it never clicked. Of course, that it could add AO into a game with no support for AO is impressive, and it looked fine in bioshock, but still. No-go for F3, even if it's not crashing for you.

If you have an ATI card it'll probably be similar, I think catalyst hooks into the desktop as well and has similar headings.

I'm not seeing anything in the catalyst control center for AO.

Anyone know if it is there. I'd like to know if it has an effect on these games too.

Oh, the last ATI card I owned was the x1300 pro - that thing couldn't have done AO if its life depended on it - so I'm not really in the know. It may be something only nVidia do. That really wouldn't surprise me, more testing with it on and off has shown that while it's often decent looking and lightweight, it's never perfect. Bioshock, for example, looks ridiculous at times as the edges of the world get AO'd, ruining the look of an endless ocean. Still, it's not something I'd considered before and may be well worth asking in cases like this, where the crashes seem nonsensical.

Don't think so, I don't have it either