My (new) refurbed 8gig black nano has been plugged into my iMac for about 24 hours now, but still says 'do not disconnect' on the screen. I have not tried to sync music to it at all, I just wanted it to fully charge. It is plugged into the USB 2.0 port on the back, but not directly... I used this short USB cable that came with one of my memory sticks. I leave that dangling around so I don't have to get up and plug anything directly into the back of the computer everytime I need to... I've never had a problem using anything with the extension cable before. Anything I should try before disconnecting it?