Possible longshot, you might try deleting the video.cfg file in the aces high settings directory. What this will do is force AH to prompt you for screen resoluton and color depth upon next starting of AH.
It's also HIGHLY possible that the GF2 tweak utility has overclocked your video card memory or processor clock too high. This almost always results in a dump to desktop or lockup.
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bloom25
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THUNDERBIRDS