Thanks for the reply, sircabulon.

I think you're right - the card is toast. I tried it again in the 66MHz slot, and this time I got some video, but it was the same corrupted video I get in the 33MHz slot (and in the beige G3).

I inspected the card and could find no visible broken solder joints, but there's probably something busted somewhere.

Oh well; time to troll my local Craigslist and Freecycle for PCI video cards or busted G3s and G4s with good cards in them!

M