Perhaps there’s a filesystem error which is preventing the Fuze+ from reading your files. Your computer has a much larger “brain” than the device, so it can probably handle these errors, unlike your Fuze+.
I would recommend running a chkdsk on your card, and see if that helps.
Also, if your using a card with a class of 5 or higher, you might consider getting a lower-class card, as higher classes have been known to have problems.
If all else fails, perhaps the Rockbox firmware won’t.
