Don't quite recall when this started behaving like this but Gnome's Nautilus has been reporting a sort of 'ghost' partition that's labeled the same as the regular one:
The partition resides on a RAID1. Clicking on the 'ghost' partition provides:
mount: /dev/md127p1 already mounted or /media/Music_Library busy mount: according to mtab, /dev/md127p1 is already mounted on /media/Music_Library
# / was on /dev/sdh2 during installation UUID=15bb606e-54af-4fa3-8341-12824a404dae / ext4 errors=remount-ro 0 1 # /home was on /dev/sdh3 during installation UUID=9eed87ee-f9d5-47c7-91e5-b82696142f7e /home ext4 defaults 0 2 # swap was on /dev/sdh4 during installation UUID=27f06259-705d-48ba-83d6-3e1837a87198 none swap sw 0 0 # Music RAID UUID=d10e627b-6068-4734-9111-5e2f71dbbe4f /media/Music_Library ext4 auto,user 0 1
I'm running 12.04.