Comment 11 for bug 1242321

I changed the title since the bug is affecting 14.04 too.
here's my dmesg:

[ 943.570033] usb 3-1: Disable of device-initiated U1 failed.
[ 948.574074] usb 3-1: Disable of device-initiated U2 failed.
[ 948.686722] usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd
[ 948.703427] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ec22a360
[ 948.703432] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ec22a38c
[ 948.703748] xhci_hcd 0000:00:14.0: WARN Set TR Deq Ptr cmd failed due to incorrect slot or ep state.
[ 961.460475] usb 3-1: Disable of device-initiated U1 failed.
[ 966.464520] usb 3-1: Disable of device-initiated U2 failed.
[ 966.577174] usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd
[ 966.593859] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ec22a360
[ 966.593864] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ec22a38c
[ 966.594180] xhci_hcd 0000:00:14.0: WARN Set TR Deq Ptr cmd failed due to incorrect slot or ep state.
[ 979.350926] usb 3-1: Disable of device-initiated U1 failed.
[ 984.354966] usb 3-1: Disable of device-initiated U2 failed.
[ 984.467623] usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd
[ 984.484319] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ec22a360
[ 984.484324] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ec22a38c
[ 984.484641] xhci_hcd 0000:00:14.0: WARN Set TR Deq Ptr cmd failed due to incorrect slot or ep state.
[ 984.485340] sd 8:0:0:0: [sdc] Unhandled sense code
[ 984.485343] sd 8:0:0:0: [sdc]
[ 984.485345] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 984.485347] sd 8:0:0:0: [sdc]
[ 984.485349] Sense Key : Medium Error [current]
[ 984.485353] sd 8:0:0:0: [sdc]
[ 984.485356] Add. Sense: Recorded entity not found
[ 984.485358] sd 8:0:0:0: [sdc] CDB:
[ 984.485359] Read(10): 28 00 3a 38 60 30 00 00 01 00
[ 984.485368] blk_update_request: 20 callbacks suppressed
[ 984.485370] end_request: critical medium error, dev sdc, sector 976773168
[ 984.485374] Buffer I/O error on device sdc, logical block 976773168

Let me know if I can provvide any other information.