Exact same problem with upstream 3.2.0-030200rc5-generic, and with the 3.2.0-5 Ubuntu kernel.
dmesg from upstream 3.2.0-030200rc5-generic:
[ 73.712292] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint [ 73.712995] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint [ 73.713469] sd 6:0:0:0: [sdc] No Caching mode page present [ 73.713472] sd 6:0:0:0: [sdc] Assuming drive cache: write through [ 73.714070] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint [ 73.714745] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint [ 73.715219] sd 6:0:0:0: [sdc] No Caching mode page present [ 73.715222] sd 6:0:0:0: [sdc] Assuming drive cache: write through [ 73.737920] xhci_hcd 0000:03:00.0: WARN: transfer error on endpoint [ 93.848107] xhci_hcd 0000:03:00.0: Timeout while waiting for address device command [ 114.052110] xhci_hcd 0000:03:00.0: Timeout while waiting for address device command [ 114.256102] usb 9-1: device not accepting address 2, error -62 [ 134.368089] xhci_hcd 0000:03:00.0: Timeout while waiting for reset device command [ 134.368093] usb 9-1: Cannot reset HCD device state [ 154.480090] xhci_hcd 0000:03:00.0: Timeout while waiting for reset device command [ 154.480103] usb 9-1: Cannot reset HCD device state
Exact same problem with upstream 3.2.0-030200rc5 -generic, and with the 3.2.0-5 Ubuntu kernel.
dmesg from upstream 3.2.0-030200rc5 -generic:
[ 73.712292] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint
[ 73.712995] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint
[ 73.713469] sd 6:0:0:0: [sdc] No Caching mode page present
[ 73.713472] sd 6:0:0:0: [sdc] Assuming drive cache: write through
[ 73.714070] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint
[ 73.714745] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint
[ 73.715219] sd 6:0:0:0: [sdc] No Caching mode page present
[ 73.715222] sd 6:0:0:0: [sdc] Assuming drive cache: write through
[ 73.737920] xhci_hcd 0000:03:00.0: WARN: transfer error on endpoint
[ 93.848107] xhci_hcd 0000:03:00.0: Timeout while waiting for address device command
[ 114.052110] xhci_hcd 0000:03:00.0: Timeout while waiting for address device command
[ 114.256102] usb 9-1: device not accepting address 2, error -62
[ 134.368089] xhci_hcd 0000:03:00.0: Timeout while waiting for reset device command
[ 134.368093] usb 9-1: Cannot reset HCD device state
[ 154.480090] xhci_hcd 0000:03:00.0: Timeout while waiting for reset device command
[ 154.480103] usb 9-1: Cannot reset HCD device state