I just noticed that nVidia has a list of certified power supplies for Hybrid SLi.
I have a PC Power and Cooling 750W Quad SLi power supply but it doesn't show up on the list. I wonder those PSUs have something special required for Hybrid Power to function properly. But a Power Supply is a Power Supply isn't it? If there was something to stop it from feeding power, some signal would have to come thru to the PS, but the 780A has no extra connectors than a standard motherboard and the 280GTX only has the standard 6 and 8 pin connectors.