Serious Sam test 2 and g400

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Hey all, just wondering if anyone is having the same problems i am with the serious sam test....i even downloaded the 'newscripts.zip' file and loaded it, but i still go to play and the environment flickers like hell, and it makes it pretty much unplayable. Just wondering if anyone else is having this problem...i saw the other threads and no one really touched on this, so i figured someone had to

FYI......p3-450, 128mb, g400 16mb, sb live! value, win2k pro+sp1