Graphic Issues in Boot Camp

Hi,

I've installed Windows 8 using Boot Camp on my MBP Retina 15" using Boot Camp.

I'm only using it to play FIFA 13 and Assassins Creed 3.

Most of the time it works perfectly. In Fifa I even have to cut down the FPS to 60 because I'm getting around

110-130 FPS. In AC 3 I'm getting a little bit more than 30 FPS. What makes gaming really fun.

But from time to time when I launch WIndows and want to play one of the games the Frame Rate is really low (around 10-15 FPS)

what makes gaming impossible. Even when I reboot the Frame Rate stays low. But when I try a few hours later the Frame Rate is back to normal.

Now I suspect that for what reason ever the external GPU (Nvidia 650M) is not launched or it's performance is reduced due to wrong temperature values.

Do you have experienced this problem too? Or have you any idea how to avoid it?

Thank you in advance

jonsiv