A truly strange iTunes problem

Check this out. Sometimes when I’m using iTunes, listening to an mp3 track that is numbered as track X of Y (where X is the track number, and Y is the total number of tracks on an album), as soon as it begins playing (or whenever iTunes accesses it at all, as when I right-click to change some info in its tags) iTunes clears the “of Y” file information. In other words, where it used to look like this:

It now looks like this (where I have bolded the song iTunes has accessed):

This doesn’t happen every single time I play a song whose track # is in the “X of Y” format, but for a given album if it happens with one track it will happen with all of them. If I select the album and manually change the info for all of the files to include the “of Y” info, it fixes the problem (and those files aren’t vulnerable to it later).

Does anyone out there have an explanation (or even a fix!) for this problem?

Sidenote: This is a much less annoying version of another issue I had with iTunes a few versions back, in which playing or accessing a song cleared all of the tag information, leaving me with a file named “[whatever the track number was] [whatever the track name was, limited to something like 12 characters].” I’ve got a couple thousand songs stuck in this ugly limbo and haven’t had much luck with fixing them, short of manually figuring out and inputting the rest of the info. So thanks a lot for that, Apple.