is this via usb media?
try deleting a single album and copying again. plug back into the car again and go to the album replaced. I would suggest the first album in the list or else you'll be endlessly scrolling for it. my 8V used to double add some songs and I tried deleting the folder and adding it again and then it saw there was only one version/copy of the song in the folder.
if it works, you'll need to delete all the music and then copy back over to the usb.
im pretty sure the MMI will do a quick scan of the USB Device and build a database/library of folders/albums on the external media.