It happened again, but I think I'm starting to see a pattern. My unit seemed to be stuck, unable to find satellites for over 5 minutes on Monday (12/21). The sat signal screen showed nearly-full bars for all visible sats, but all greyed out, as though it couldn't figure out what the sats were saying. So I did a full reset (15-second button push). The unit came up (after the usual long re-initialization process, displaying the welcome screen), and found its location right away.
But... no more QuickGPSFix for two days. Rather than wait until things get bad, I'll just clean it out now.
Result (drum roll please): Sync the unit again and voila, QuickGPSFix is offered for download. I'm back in business until the next glitch.
Note to Buzzerman -- I don't do anything to the folders on the unit as part of the process, and I don't reset the unit. I just delete the QuickGPSFix-xx folders in the "ephermis" directory on the PC hard drive. In fact, to be safe, I don't even have the unit connected when I make the change. I delete the files on the PC, and then hook up the unit to sync.
And something else I hadn't noticed before... the files inside "ephemeris.cab" are dated 8/18/2102. Awesome, GPS data... from the FUTURE. Too bad they didn't send back a software patch to prevent the glitch, while they were at it. I guess in 93 years, we'll still be complaining about software bugs.