Update:

The symptoms I outlined above had held true for five days. Naturally, shortly after I posted here, they changed — for the worse.

Basically, whenever the main power switch is ON, *all* the LEDs light up (still with no display or menu). It does not in any way react to my pressing STANDBY on the front panel or OFF on the remote. The only way to get the LEDs to turn back off is to switch the main power off.