Thanks all

But what ive done so far:
SuperPI
3dmark06, it also shows random results, because of the random slowdown. But a few start and stopping, will make it run normal. Usualy take 3-4 tryes.
The sins problem, seems random. At times it does close down right. But my pc gets weird, like slows down proformance (its not the same as the random slowdown i get with other games).
Used Registry Mechanic, i kinda use that once a month.
So if i get the sins "bug" and the random slowdown at the same time, games becomes total unplayable with 0-10 fps.
Only way to fix it, is a restart. It doesent help just logging off.
Ill do some further testing later today, with your suggestions