Is this something that just started happening? Or did you try using the 6950 and it doesnt work?
Just saw where you just got the Asrock. Try hooking it up to the onboard and see if it boots. If so, go into the bios and set it to look for PEG 1 on boot. Shut it back down and hook it up to the video card and see what happens. Make sure you got the PCIe power connectors plugged in.