external hard drive not detected after ubuntu crash [restarting machine]

view story

http://askubuntu.com – today i tried to watch movie [with vlc media player] from my external hard drive [expansion portable 500 GB], and it's play good, then pause the movie and play it again, and my Ubuntu crashed! [Ubuntu 12.04]i had to restart the machine, so did it, but after that Ubuntu can't recognize this hard drive! i changed USB cable but it was not effective. this is my dmesg command result : [ 191.281630] usb 2-1.3: new full-speed USB device number 9 using ehci_hcd [ 191.353527] usb 2-1.3: device descriptor read/64, error -32 [ 191.529115] usb 2-1.3: device descriptor read/64, error -32 [ 191.704669 (HowTos)