OzAndrew: I ran the AudioStar through the diagnostic cycle twice. It worked exactly as you describe except it did not reboot itself at the end, it just cycled through the keypad test again. I did not see a "Fail" on the RTS232 test, so I'm guessing the unit is fine - which is definitely a good thing.
Now I'm waiting for a new USB - RS232 cable; I should have it tomorrow.
I totally appreciate you help here. None of this stuff is in the manual.