I use Ubuntu 9.10, and the MiniSD card shows as having the space used as if there were files.

Baobab (the disk usage analyzer) shows that the card only has 118 MB used (of the 401 Ubuntu claims there are).

Of course, I already tried the obvious (rebooting the phone, adding and removing files, etc.), but I don't want to format my card, because I still have some files on it, the transfer to my computer is slow, and because I use an old wire it fails often.