IPod 2ndGen,works in iTunes,doesn't work after disconnecting USB

Hello,

My iPod Nano 2nd gen doesn't work after disconnecting the USB wire from my laptop.

Model MA477ZP, Format Windows, Latest iTunes and iPod Software

Otherwise it said full charged once, syncs properly, was able to add music.

After selecting Safely Remove Hardware from taskbar, I'm able to access the iPod and play music from it, only when it is connected to my laptop through USB.

If I remove the USB, it just dies (screen starts fading) and doesn't respond to system reset.
And when I reconnect the USB, Apple icon appears, then gets detected by iTunes and says Do Not Disconnect.

It was sitting idle for quite some time before I tried all this.

Don't know what to do!
Any help would be great as I have no idea what is wrong!!