This, my friends, is the point at which I back EVERYTHING up and wipe the drive. And this is what I spent a day and a half doing shortly after my last entry.
My original plan was to do a full backup and reinstall anyway once I got the new OS X installation discs in the post, but that plan was brought forward when I saw the above message. It's not gone so badly, in retrospect: I was back on-line last night, most of what I immediately needed already installed. Now all that's left is a couple of the apps I don't need, plus a re-install of OS 9.2.2 for Classic's purposes.
Fingers crossed, version 10.2 will serve me longer than the public beta and versions 10.0 and 10.1 managed. Which reminds me, I need to turn on Journalling. (How appropriate.)