Won't play on Bose Sound dock, not keeping charge

For some reason my nano played fine on my Bose sound dock for about a week, then stopped. I've tried other ipods with the Sound Dock and they work, so I know it's my nano that has the problem. I kept it on the Sound Dock to charge over night and the next day took it to the gym. The battery died quickly. Anyone with similar trouble or suggestions?

Ipod nano