Well, I did uninstall FireFox and then reinstalled from scratch. The second time it "took" and now I've got FireFox 2 working just fine at home. And my vanished bookmarks, which I was afraid had been annihilated, reappeared, so I'm happy.

Now, the first time I installed it, I just ran the installation over top of my FireFox 1.5.whatever. I also installed a couple add-ons, which I've not tried to install again, so the snafu may have had something to do with either of those things. But your guess is as good as mine.