Everygame I have for some reason locks up on me. Madden 08, Bioshock, Counter strike source, prey, halo 2. I just received my video cards yesterday from an rma from sapphire. I am running windows vista 64 bit ultimate. System specs: q6600 @ 3ghz, 2x2900 xt 512 mb, 2x1gb pny ram ddr2 1066, raptor 150 gb, creative sound blaster elite pro, dell 3007wfp, and silverstone 1 kilowatt psu certified for crossfire with 2900's. Any help is greatly appreciated, but my gut feeling is the cards are what the cause is or could it be the motherboards pci-E slots? ohwell I dont know but any help is very much appreciated thanks.