I have an ati 9600xt. I have played doom all the way through on high setting. Recently I upgraded to a 64 bit system and reinstalled doom just to see how it played. while trying to overclock my video card again, all of the sudden it won't let me put it on high without set up screen going fuzzy. I have to put it on medium to make it clear again. As far as I can see I haven't changed any settings and have tried everything to get it right. Has anyone had such a problem?