It sounds like there might be a problem with your video card then. Are all the pins fine? Could possibly be a short? Did you try updating all of the drivers for it? and finally what is your video card?

Have you tried gently removing the vid card and replacing it? It may just need to be reseated.

Or, this could very well be tied into your failing power supply. Can you get another one relatively cheaply to see what symptoms you experience then?

Did you build this PC yourself or was it pre-built?

And be careful updating your BIOS. One wrong move and you have a very nice, powered paperweight...