Just Cause delayed stuttering

[Aceindahole]

I just recently bought this great game over the past weekend when it was on sale on Steam. When I play the game, I will play without a hitch for about 20 minutes and then randomly the game will slow down extremely (to the point where it isn't playable, about .2 FPS), the sound will flicker and everything will obviously be slower, like the Esc menu or PDA. I have verified the files on Steam and ran a Defrag on the files a few times over. I have an almost new computer that exceeds all of the minimum requirements for the game, and even (according to Can You Run It) would be able to run the game on maximum settings, but to keep it from stuttering I turned all of the Video options down. I looked on the forums and didn't see anything like this problem happening, any idea what it could be?

Thanks!

Edit: Also, with this problem, the game does not actually stop responding (like when I go to my control panel and try to force close it, it will be very responsive), so I can't give you guys any type of error message.