Amazing this thread has been brought back from the dead!
My experience in solving this (Or it solving itself) is the same as Mikan's
ok!!! Solved!!! Put the sli selector back in after shutting down from booting from having the selector card out and bingo!!! So probably the bios was looking for an sli config from my previous setup and not seeing the card selected as single. Stupid selector cards.
I didn't have an SLI setup, but booting without the selector card and then rebooting with it in the correct position seemed to work, eventually. It's the only thing I can think of that may be the fix as I was messing about with this for days, tried loads of configurations and installing both the selector and 8800gt card in and out (and almost in the bin!).
Sorry I can't be of much more help, I can't replicate it again as I've gone over to the red side for my gaming rig and don't have the 8800 either...