Very good idea, but apparently not the problem.
My techie fooled around with it yesterday and reported something about modifying the BIOS "to PCI" instead of "AGP." He also swapped out the AGP primary card, although I had done that before to no effect.
He seemed to think a power surge might have caused it to revert to an older BIOS setting. Frankly, that doesn't make any sense to me, but it's working OK. Probably there was an issue with the power management or config, as suggested above, and in all the board swapping, etc, it got reset somehow.
anyway, it's working. Thanks for suggestions.
PS. I googled this issue and there were an incredible number of hits. Apprently it is far more common than yu woul dexpect. Other than the battery issue referenced above, I really never saw a logical explanation in all the comments that were linked.