Battlefield 3 started to stutter terribly in Bootcamp Windows 7

Hi

I'm hoping someone could offer a suggestion

I bought a new 27" imac, with the 780m I have 24Gb ram and I loaded windows 7 via bootcamp.

I loaded Battlefield 3 and was in the middle of playing the single player campaign. All was working great, I was running ultra 1080 @ 55-60 fps or ultra 1440p at around 30-35 fps. The game run really smooth with no lag or stuttering.

After not playing the game for about a week (because I've been using parallels to access windows) I fired up the imac in windows 7 via bootcamp and Battlefield 3 just stutters. It goes from 60 fps to 2 back to 60 every 5 or 6 seconds. It really makes the game almost unplayable.

I've tried some tricks like making the prerendered frames equal to 1 but that didn't help.

I made 2 changes that I can think of but I don't know if either of these things would cause the stuttering problem.

• The first change I made was upgrading to Mavericks, but I don;t know if that would effect the Windows partition (I booted 100% into windows so Mavericks wasn't loaded at all)
• I added a Time Capsule as my backup and wifi network. I turned off the wireless router of my cable modem and now I use the time capsule exclusively for wireless internet access. (Although I've only been playing the single player game so I don't know if that would have anything to do with it.)

I am new to the mac and there might be a simple thing that I just don't see. It ran great for the first couple weeks but now it stutters horribly.

Any help is really appreciated!

Thanks.