Long story short, I've started an OS reinstall on my NV+ and it's been sitting as "Reinstalling FW Please Wait..." for over an hour. How long should it take? It doesn't sound like the drives have spun up, as far as I can tell (but I could be mistaken).
The longer story: the USB drive to which I was backing up appeared to spontaneously disconnect a day ago. I tried to shut down, but it couldn't abort the backup. Even shutting down by the front button hung. Unplugging the USB device didn't help. Blue power LED and drive lights had turned off, but the LCD still said "Shutting down...". So I unplugged it to really shut it down.
To follow up with the conclusion, we tried going into tech support mode without any drives at all, but that hung as well at "Tech Support Please Wait..." Apparently that should always work. That was the clue to try a memory test.
Very early into the first test (I think verifying pattern 1), the RAM failed. After 7 years of use.
After replacing the RAM (and testing it several times), the system just booted up. Apparently with the bad RAM it had been hanging on everything, so thankfully the OS reinstall never even began.
