iPod Nano 6th Generation can't be restored, error code 1439...need urgent help>>>

I haven't recharge my iPod for about 5 days. Then I plugged it into my laptop yesterday. For the 1st time it just showed the Apple logo and slept. After a while it has showed a white screen saying, "Do not disconnect" and also a forbidden sign(ø) have been blinking. Itunes says, "iTunes has detected an iPod in recovery mode. You must restore this iPod before it can be used with itunes." with an 'Ok' button. I've tried for several times but it can't be restored. Finally, itunes shows an eror message saying, "The iPod 'iPod' could not be restored. An unknown eror occured (1439).".