Hah! I wrote that as though folks were hanging on my every word. The continuing saga of Rivet's quest for a perfect picture.
Having put in an AGP upgrade card, the picture was okay, but very slow to paint...sometimes. Hitting it with its own PSU seemed to do the trick. However, I just happened to notice that the BIOS was set to PCI.
I elected not to mention the fact that I hadn't noticed that. Well, the PSU did seem to be the issue. But then I put the BIOS to AGP. Power okay, and the right slot selected, now we're cookin'.
Nope, it was slower.
I put it back to PCI, and it was back to its improved state.
In an uncharacteristically modest moment, I bellowed to everything listening - namely the cat - that I hadn't got a clue as to what was going on.