I have same bug with Lucid LTS, too.
It could be seen on screenshot attached.
** Attachment added: "Screenshot.png"
http://launchpadlibrarian.net/48121340/Screenshot.png
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Error detaching: helper exited with exit code 1: Detaching device /dev/sdb USB
device: /sys/devices/pci:00/:00:
My external drive is formatted by FAT32 but the same problem occurs.
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Error detaching: helper exited with exit code 1: Detaching device /dev/sdb USB
device: /sys/devices/pci:00/:00:04.1/usb2/2-5) SYNCHRONIZE CACHE:
FAILED: No such file or directory (Continuing despite SYNCHRONIZE CACH
