This has happened to me a few times, mainly when I power down my iPod. To resolve you need to hard reboot: Press and hold the top "power button" and the center "control button" at the same time. In less than 30 seconds a screen with the Mac apple will appear as the system reboots. When finished, it will take you to your password screen or straight to your main page, if it is not protected.
The hard reboot does not effect any of your apps or anything else on your iPod. It's just like restarting a PC that has crashed.
The hard reboot does not effect any of your apps or anything else on your iPod. It's just like restarting a PC that has crashed.