Extrait de la commande dmesg :
Apr 16 18:26:46 localhost udevd[12809]: failed to execute '/lib/udev/mtp-probe' 'mtp-probe /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1 1 124': No such file or directory
Apr 16 18:26:47 localhost kernel: [4926459.870377] sd 111:0:0:0: [sdf] Asking for cache data failed

Résolution :

• installer le paquet libmtp-runtime : aptitude install libmtp-runtime

Source : http://crunchbang.org/forums/viewtopic.php?pid=293994