Yeah, I see the word "recommended" when it says single card in blue slot - not the word "must", so either should work.
Two cards, yes, they have to be bridged to work as dual - but it *seems* that plugging anything into the black socket kills the whole system (hence the guru feeling that the mobo is faulty).
Yes, both need to run at x8 (and the blue is a x16) - not seen anything, anywhere, on how to change the rate. I've certainly not done anything deliberate.
Running fine as a single card - although only feeding one of my two monitors (both plugged into the single dual DVI card in the blue slot).
Vista is being sucked from the DVD drive and being laid out neatly on one of the hard drives.
We are getting there.