I have an i5 2500K and nvidia 9600 GT with proprietary driver. For some reason, this set up on 12.04(and was same on 11.10) seems to work fine on boot up, but after about 30 mins of use, games and other accelerated surfaces start running at about 5fps. This is fixed by a reboot to start it all over again. Is there some way I can get rid of this, as I don't have this problem with other systems with Ubuntu?