Lock up playing BF3 multi

Sorry if this has already been asked, I did a quick search but nothing was exactly like what I'm getting.

So I bought BF3 figuring my iMac was quite above the recommended and I run bootcamp for a few graphic intensive pc games and never had an issue at all.

My iMac is the 27" 2010 model with the core i-5 (2.8ghz I believe) quad core, 4 gigs ram ddr3 and the ati hd5750.

If I leave the standard drivers windows 7 insists on I keep getting an error message that my drivers are version 10.4 and BF3 requires at least 11.7.

Ok...so let's update.
Well no matter what I do the game locks up always after about 20 minutes (only playing multiplayer don;t care about the single at all.)

I ran cpuz and core temp, nothing gets above 70 degrees celsius, but it locks up, so no over heating issue I guess.

Anyone figured out how to get this to run with out freezing?
I'm thinking I just threw away 60$ now... And this is why I switched to apple and console gaming all those years ago

Thanks