Reset Your iPod Touch's Settings
If neither of those works, the next place to start is resetting all of the settings on your device. Go to Settings -> General -> Reset. There will be a few options, but tryReset All Settings first.
Factory Reset Your iPod Touch
If all else fails, you may have to restore your device to factory settings. UnderSettings -> General -> Reset, select Erase All Content and Settings to restore your iPod back to its original, out-of-the-box setup.