Not sure if it’s related…
I had a similar issue with ATI Radeon GUI card, 2 RedRockets, 2 Quadro 4000’s and a GTX 285. My machine would actually Kernal panic when booting up. If I took one of the Red Rockets or the 285 out, it worked like a charm. As soon as I had all the cards in there, it would kernel panic.
When using either the nVidia 285’s or 4800, the DaVinci configuration recommends that you use the nVidia GT 120 as the GUI card.
I replaced the ATI RDadeon HD 5770 with the GT 120 and the system worked with all other cards installed.
Not sure if this is the same problem, but maybe you could try putting a GT120 in there and see what happens.
Craig