cut and paste of my reply in general hardware...
hi,
i have a bfg 6800gt and was getting exactly the same type of distortions. i ended up rmaing the card to bfg twice and the returned ones showed the same distortions. especially in hl2 and farcry.
to make a really long and painful story short, nothing i could do would make it work on the 2 motherboards i tried. 450w fortron source power supplies, fresh clean installs, all of the available drivers from nvidia and guru3d, all of the bfg tech support advice. the strange thing is that i also tried a evga6600gt and a msi 5600 ultra in the same computers with the same drivers and they worked just fine.
i finally got it working (mostly) in a asus a8v deluxe with a a64_3200 and a coolermaster 450w ps. the motherboards that it gave problems in were a chaintech and a gigabyte (both more than 1 year old).
i'm not sure what's going on here but i'm not happy with this purchase, and if i wasnt able to get it going in a motherboard i already had, i'd be looking for my money back.
edit***************************
this is the distortions i get in farcry
here