Try:
- Reset the iPod. Nothing will be lost
Reset iPod touch: Hold down the On/Off button and the Home button at the same time for at
least ten seconds, until the Apple logo appears.
- Restore from backup. Place the iPod in Recovery Mode if necessary to allow the restore.
- Restore to factory settings/new iPod.
- Make an appointment at the Genius Bar of an Apple store.
Apple Retail Store - Genius Bar