Kunix, thanks for the info. I reinstalled the drivers from the link you sent, and rebooted my machine.

Let's try the Safe-Boot thing. Since I have a 100% working Zumo 660 as well, I tried the method you outlined. Here are the steps and my observations.

1) Completely power down the Zumo
2) Press lower left part of LCD screen.
2.5) Open battery door to gain access to USB port on Zumo.
3) Connect the device to the PC.
4) Press power button and the following happens:

Garmin splash screen appears, keep holding LCD and power button.
Screen calibration dot appears in center top of LCD screen.
Calibration dot disappears and Garmin splash screen appears again.
PC picture indicating it is connected appears on LCD, along with the green progress line.
Progress line completes.
Garmin splash screen with PC picture.
Still cannot see the unit in updater.exe.

Again, this is with the 100-percent working Zumo.

When I try your method with the defunct model, the Garmin splash screen appears, and stays once I have it hooked to the PC. But nothing else appears on the screen.

Again, thank you.