I believe I've figured it out...

A month or 2 back I installed a logo slice from the TivoCan guys; figured some of the logos might match up (Disney, Disc, etc). Given that I knew the problem happens with a fresh install after running guided setup, I ran a clear/delete all this AM, moved that logo slice out of the Headend dir on the emulator, tried again, and all is well now.

Of course, the bad thing is that everybody's gotten that slice, and presumably it's b0rk3d their tivos. I dunno if it's possible to get rid of it with anything short of a clear/delete all, but if anybody's considering nuking their box perhaps they could do some experimentation before a clear/del all (in the restart area there are a few other options; in fact, doing the "run guided setup again" might do the trick, or one of the others like nuking season passes).

Sorry folks, I know this is experimental stuff, but I still feel bad when I b0rk something.