One common problem with the iPod nano is that the device can lock up. You can fix this problem by simply resetting it. To reset your nano, follow the steps below in this Tech-Recipe.
1. Verify that the device does not have the Hold switch engaged. (If it does, this could be the problem.)
2. Press and hold both the Menu and Select buttons at the same time until you see the Apple logo appear onscreen.
This will not delete any of your songs or files; however, you may lose some of your custom settings.