Guys and Girls:
About these "frozen Zumo" issues - I have seen this reported in a number of different posts here, but I have never ever had this problem myself, despite riding about 8,000 miles now with a Zumo, using all sorts of different software.
One thing that Zumo users need to be aware of is that the Zumo reacts very differently than all the previous Garmin GPSRs when it is connected to a computer using a USB cable. Since the invention of the first Garmin GPSR (that had a USB connection) about 7 years ago, you could just plug the GPSR into the computer and unplug it at will. The GPSR didn't take much note of the computer, it only interacted with the MapSource application, and nothing else.
Since the advent of the Zumo and other Garmin GPSRs that share the same user interface as the Zumo (C series, for example), the relationship between the computer and the GPSR has changed dramatically. Now, when you plug the GPSR into the computer, it behaves exactly like any other USB mass storage device. In other words, the computer mounts it as a single disc drive - or two drives, if you have a SD flash memory card in your GPSR - and the computer takes over total control - and I mean TOTAL control - of the GPSR.
I'm not entirely familiar with the technical reasons for this change in behaviour, but I do know that users now have an obligation to 'properly' dismount the GPSR from the computer before yanking the USB cord out of either the side of the computer or the side of the GPSR. To properly dismount a USB device, you go to the 'Safely remove hardware' function of your Windows operating system, and select the option to remove the GPSR. This action is known as 'dismounting' the device.
I encountered quite a few lockups of my Zumo 'at my desk' the first week I had it, because I was treating it like every other GPSR I had owned for the past 5 years (SP III, 26xx, 72xx, Nav I, II, and III, etc.) and just yanking the USB cord out of the device when I was finished with it. The GPSR doesn't like this at all, and I am going to guess (emphasis: guess) that this might be causing some corruption within the device that is then causing the power on / power off problems down the line.
The reason behind this guess is pretty simple: Since I started properly dismounting the device, using the "Safely Remove Hardware" function of Windows, I have never experienced any flaky behaviour or lockups from my Zumo.
Hope this info will help the rest of you. I'm not suggesting it is the solution to every problem everyone has ever reported, but I do think it might be the cause of some of the lockup problems that have been reported.
Michael