USB music player not recognized as one, it is recognized as a flash drive instead. Probably is the player. Same issue as CarlaSella, but i think is not a bug, but an sort of protection of bootable USB drive. Tried with several different flash drives and worked fine (See Bug #762018).
When i insert a usb key, it get's mounted correctly, the correct icon on the desktop and in the launcher appears, but nautilus does not open to show it's content