Automatically generate playlists for folders

At least that’s what it seems to me. I use AutoM3U to create playlists for my Clip. The music is organized this way on the Clip:

\MUSIC\folders\mp3 files under each folder

When using the Clip to select and play music, all the playlists (with names of the folders) contain their mp3 files except one which displays as “Empty”. I’ve looked at the contents of the clip on my computer and everything seems to be where it should be including the mp3 files under the supposedly empty playlist-folder. As a clue, that empty playlist-folder is the last folder (and files beneath it) that I put on the clip.

Any ideas?