Hey, thanks for the replies.

I have come to the conclusion that the finger-in-the-upper-left thing works with Nuvi units only. I have tried it on my friend's good Zumo 660, and it doesn't get into pre-boot when I touch the upper left part of the screen.

USB drivers are good. I can see all my files in the Garmin folder on the unit -- including hidden ones. Plus, Webupdater, and Garmin Communicator both see the unit. I can see it in OSX, and in the Windows 8 VM through Parallels. I just can't see it through updater -- even with the finger trick.

When it is plugged in, all I see is the splash screen I loaded into the logo.bin file originally. There is no progress bar, or indicator that it is plugged into a computer.

Like I said, I am at a loss because it is exhibiting some bizarre behavior.