Video card died
The fan on my PC's video card got gunked up, made funny noises for a few weeks (which I stupidly ignored) and then eventually FELL OFF the video card onto my sound card. Kerplunk. The plastic clip holding the fan where it was must have melted.
The video card eventually died once the GPU fused to the silicon. I'm surprised it didn't start a fire.
So, knowing I want to [eventually] get a Mac Pro as a permanent upgrade path from my PC workstation, I wonder if I should spend any more money to repair it. Something very powerful and genetic is stopping me from spending $30 and getting a crap card to replace my Radeon 9800 Pro. Logic would say that's what I should do.
But you know me.