Well, I was getting some nasty errors on my CDROM recently while trying to play a CD that I knew worked before. XMMS just hung there, while xconsole showed errors about "SeekComplete DriveReady Error".
So I rebuilt my kernel with only the drivers I actually use (removing the swsusp patch that makes my machine panic if I try to use it) and that didn't work.
I installed ALSA (which debian have now got quite a nice build process for now, I think, although I hacked it about a little bit). The sound quality is absolutely loads better, but it still hung on the "bad" files.
I searched around the net a bit, confident that my system was fairly neat and tidy now. Someone mentioned that they see that error when the CD is scratched.
I took the CD out, polished it with the "Magic Cloth" I use on my glasses (3 pounds or so from Boots Opticians) and now it works.
Ooops.