Ha! I had that exact problem with my Asus 650i SLI motherboard. Plug your monitor cable into the other connector on your video card. I had 2 8800's as well, in SLI. That means there are 4 possible DVI ports, and any money says you have picked the wrong one. Just unplug your DVI cable, and try another port until the monitor comes on. Make sure you give each port 15 seconds or so to realize there is now an LCD connected to it.