Although a slightly different issue from what you are seeing, I recommend trying this troubleshooting assistant to see if it helps:
The article I found the assistant from may also be helpful:
I have something simaler to this with ym 7th gen (extreamly cool) and it disconnects a few seconds after plugging it in. on and off. On and off. I tryed using other devices and the are the same. its not to severe (it only happens 50% of the time) but the device is only 2 or 3 months old and its really anoying.
An easy solution would be nice, as im only 11, and dont have a lot of stuff on my hands.