Thanks for the tips!

I power cycled again and unplugged power cable for several minutes. Rebooted and it came on and works fine! During the time that it was not working, pressing Display also did nothing. Have not retyped it, but may do so just to be on the safe side.

It all seems fine now, but I'm worried that it's going to start acting up. May be a good time to think about upgrading since the 568.1 is getting a bit long in the tooth. The G61 looks reasonable in terms of functionality that I require and price (used) - altho, I hesitate giving up the balanced analogue outs to speakers. The G68 has too big of a form factor.

Can the G61 be programmed with a USB cable, rather than serial?

iMac --> ATV --> 568.1 --> M33 LCR + M555 --> AIM8Five + B&W PV1 + Panny 50" HD
iMac --> Apogee Duet --> Neumann KH120A
Anapeg SD11 Pedal Steel Guitar --> Hardwire RV7/DL8 --> Telonics FP100 Volume Pedal --> Little Walter Tube Amp --> Telonics Cab + Eminence EPS-15C