Damn it, I suck.
I thought I had fixed the last of the mysterious things that led to weird CD unmounting bugs for Red Hat Linux 8.0. These were caused by combinations of bad CD burns, bad CD-ROM drives, and the CD-Rs not wanting to be read by the CD-ROM drive.
Well, I was right. I fixed the cases where unmounting would fail. Unfortunately, it uncovered another case in there that's been broken forever. It's just never been visible before, because you'd always hit an earlier bug first.
Damn it all to hell.