ATI 5770 Stutter/Heat Problem? Help!

Hey everyone, I know this is my first post but I'll try to give you as many details as I can for the problem.

So I received an ATI 5770 for a Christmas gift this last Christmas and it seemed to be working amazingly. It was the MSI Hawk edition card in which I bought for its overclocking abilities. Once i got the card I plugged it in and put a small clock on it (i believe it was 925 core and like 1250 on memory) and everything ran flawless. However in the recent few weeks it has been acting up quite a bit while playing the more demanding games like DiRT2 and Stalker : Call of Pripyat. The game would run fine for a few minutes and then I would get a microstutter, and then it would run fine again, and then another microstutter and so on. I took the card out and blew some air through it thinking it was a dust problem and the card was getting too hot but that wasn't the case. After looking at HWMonitor and GPU-Z for temperatures, during these games the card would run upwards of 60-64c with both games on max settings at 1080p. Figuring something went wrong somehow I lowered the settings on the games and was still getting the same problem. I also took the small overclock off to see if that was the issue and I was still getting the same problem. The drivers for the card are updated to the last ones available as well. I just don't know what's causing this as before the microstutters were happening the card never reached 60 degrees c on each game.

I'm running Win7 64bit, 4gb Patriot RAM, AMD Athlon II x4 630, and the MSI 5770 Hawk, all on an ASUS Mobo for specs.

If anyone can help me with the problem or steer me into the right direction I'll be quite a happy gamer again  . Also, if anymore information is needed, please just leave a post and I will give you what is needed. Thanks!