Strange lag when turning the camera too fast

[duktap]

Ok so as the title say, when I move the camera too fast using right click, I get some kind of lag, or chokes. If I go slowly, everythings is fine. If I move straight ahead, I get no lag, the game run smooth at all time. Its only when I turn the camera too fast that it happens. I tryed lowering my graphics but it wont change anything. Actually, I got a monster of computer so im pretty sure its not my computer the problem.
Am I the only one who got this problem? and is there a way to fix it?
Also, I got the mouse problem that when I move it too fast it lags out but I got this fixed by putting Hardware mouse...But if there would be a way to use the ingame mouse without lag then it would be great!
Thanks a lot for the help and sorry for my bad english :X

[Zerlin]

After talking with Duktap in klients we have determined that his video cooling fan is almost dead.