Problem solved.
I've scanned my pc for some virus, it has found 2 worms.
+ couple days later my videocard's blower was broken, so it could be the worms, or the overheating videocard, i guess the last one, how longer i play the game, how more the grapics turned weird, until the pc crashes, (graps didnt go weird with gw, only with oblivion^^) thx to a new blower on my vid card the pc runs without crashing etc.:d