I wonder if this means the disk is going bad... *sob*
Update: The Tivo is dead. Long live the Tivo.
I tried a bunch of things, and eventually did a "factory reset" to see if that would fix it (basically wiping the disk and starting over.) When reinitializing, it got stuck at 28% every time while "contacting satellite". I actually called tech support and they had me try a few other power-cycley voodoo tricks, but finally the guy said, "you're screwed, man. It's dead."
So I got a new one (series 2.) Maybe I'll recycle the old one as a kiosk for the club...
Apparently the USB ports on the new models aren't really used for anything; you can put an ethernet on it and will (soon) be able to use your Tivo to stream MP3s from a file server, but what good is that, really?
My agent inside the Tivo Collective tells me that getting a shell on a series 2 requires opening the case and mucking around, and isn't worth it anyway because there's not actually interesting you can do with it once you do.