Dual Monitor Problem

I have a strange problem where my video card (ATI HD2600XT) has stopped sending an output to a second monitor. This happens at startup/POST before Windows loads, so it isn't a driver issue. If I unplug the monitor and cable from the first DVI output on the video card and plug in a different monitor and cable into the second DVI output on the video card, then that second monitor gets the signal. That rules out the monitors, the DVI cables, and the outputs on the video card. To be clear, either DVI output on the video card works, but just not at the same time.

I’ve tried reseating the video card, and also moving it to the other PCI-E slot, but that didn’t change anything. I’ve tried buying a new video card, and again…same results. My motherboard (Asus P5KC) does not have onboard video, so there is nothing that I can really change in the BIOS. I’ve tried unplugging the case power and plugging it back in.

I’m stumped. I’ve had this problem once in the past. It lasted for several weeks. One day, both monitors came back and I wasn’t sure what changed. It has run for several months without issue, and the other day reappeared after I reinstalled Windows. Again, this problem occurs before Windows loads, so it isn’t a Windows problem. I’ve also tried several versions of ATI drivers.

Another strange symptom is that every now and then my machine locks up and when I reboot, my BIOS has forgotten it’s settings. I’m not sure if that is a clue or not.