Once I decided the problem was that the BIOS wasn't setting up the AGP address correctly (@0xb8000000, which was unaligned), I reset the BIOS to defaults, and reconfigured it. Reboot, Bingo! the card came back at 0xc0000000. and now glxgears is running @7800fps.
Thanks for the help. Iím in your debt.
We should all a FAQ about common (and less common) problems and how to solve them.