Well, this is weird. On a whim, I left it on all night and tried it again this morning. Still no dice. So, I replaced the video card (Rage 128 from a B&W) with my Radeon 7000 and it booted, but now I am not getting any response from the screen at all. It no longer comes out of standby even briefly like it did before. I'll try another Rage 128 and also try using the lower bank of PCI slots rather than the upper if just replacing the card doesn't work.