I've been switching back and forth between the two USB-modes, trying to find the right mediaplayer for handling my MP3s and transferring them to my Fuze.
Today I noticed I had two versions of certain MP3s on my player, so I connected the player to my computer (Windows XP) to delete the duplicates. But I could only find the files one time on the player.
I ended up deleting the folder that contained all the number by the artist, including the artists-folder, checked that it was deleted, and disconnected the player.
Much to my amazement, when the Fuze restarted, the player still showed the songs on the player, but this time, only once.
Then I tried switching USB-mode, and suddenly both the artist folder and the songs was visible on the computer!!!!
Looks like some files are visible only in MPT mode, and other files are visible only in MSC mode.
This goes for both songs, folders and playlist.