Je viens d'avoir ce problème
Pour moi la solution a été un fsck sur la partition :
fsck /dev/sde1
dmesg me donnait ça :
[ 4336.313712] usb 4-3: new high-speed USB device number 3 using ehci_hcd
[ 4336.927046] usb 4-3: New USB device found, idVendor=05dc, idProduct=a209
[ 4336.927053] usb 4-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 4336.927057] usb 4-3: Product: USB Flash Drive
[ 4336.927061] usb 4-3: Manufacturer: Lexar
[ 4336.927064] usb 4-3: SerialNumber: 000000000000000000
[ 4337.141249] Initializing USB Mass Storage driver...
[ 4337.141477] scsi18 : usb-storage 4-3:1.0
[ 4337.141600] usbcore: registered new interface driver usb-storage
[ 4337.141604] USB Mass Storage support registered.
[ 4338.330924] scsi 18:0:0:0: Direct-Access Lexar USB Flash Drive 8.07 PQ: 0 ANSI: 4
[ 4338.331894] sd 18:0:0:0: Attached scsi generic sg5 type 0
[ 4338.333316] sd 18:0:0:0: [sde] 30662656 512-byte logical blocks: (15.6 GB/14.6 GiB)
[ 4338.334436] sd 18:0:0:0: [sde] Write Protect is off
[ 4338.334443] sd 18:0:0:0: [sde] Mode Sense: 23 00 00 00
[ 4338.335486] sd 18:0:0:0: [sde] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[ 4338.875842]
sde: sde1
[ 4338.879531] sd 18:0:0:0: [sde] Attached SCSI removable disk
[ 4339.194868] FAT-fs (sde1): utf8 is not a recommended IO charset for FAT filesystems, filesystem will be case sensitive!
[ 4339.244967] FAT-fs (sde1):
error, fat_get_cluster: invalid cluster chain (i_pos 0)
[ 4339.244973] FAT-fs (sde1):
Filesystem has been set read-only
[ 4339.405048] FAT-fs (sde1): error, fat_get_cluster: invalid cluster chain (i_pos 0)
[ 4506.074537] sde: detected capacity change from 15699279872 to 0
puis la clé s'est montée en lecture/écriture, mais le navigateur de fichier ( caja pour moi ) ne peut toujours pas écrire un fichier, bien qu'un terminal le peut
j'imagine qu'au reboot j'accèderai normalement à la clé