If you're into gaming in general, it may be worth while replacing your video card with on intended for gaming. you'll be much happier in the end.

That came into my mind first, but I think the 9600GT is indended for gaming...I will continue to monitor the temps while playing, the problem was absent today. 8)I'm also considering a slot fan, it is cheap and what can i lose? On the other hand it might be the room temp causing these symptoms, as the weather turned colder, and no heating in my flat yet, there were no heatspikes today. I also decreased my settings, and the game is still enjoyable.I think I'll open a new thread in the hardware forum, as my adventures showed a few new things i should investigate.Thanks for all the input, i've got a lot new info from all of you!

UPDATE:The problem was caused by the unlimited framerate, which caused overheating even at low settings.For all who are looking for help in the same matter:keep GPU temp under 70-75C hangups and texture problems start at 80C.Happy flying!