I reversed the last of the changes I made, and that problem has now gone away.

The change? This AMD motherboard keeps the USB3 ports active so that users can charge external devices up to three amps (!) while the computer is shut down. I thought, "Aha! Maybe the USB2 ports don't have this feature," so I moved my cable that feeds my USB hubs to a USB2 port, only to find that the USB2 ports also stay active after shutdown.

This morning I remembered moving that cable, and put it back into the original USB3 port, and the bootup sequence returned to its original display.

So, after hours of testing and fiddling around, I am now back to exactly where I started. Sigh...

Oh, wait -- I just discovered another power-related anomaly. I just assumed that the LEDs on my keyboard (programmable, full of electronics) stayed on because they were like the LEDs on all the rest of the my USB stuff... until I realized that my keyboard is PS2. So apparently my PS2 port stays hot on shutdown as well. I am becoming significantly disenchanted with this motherboard! It will be no contest if I have to make a choice between keeping this motherboard or preserving my virtually irreplaceable AnyKey keyboard!

tanstaafl.