Bad bits sometimes happens. If it recurrs try in order:
Reset iPod touch: Press and hold the On/Off Sleep/Wake button and the Home
button at the same time for at least ten seconds, until the Apple logo appears.
- Restore the iPod from backup
- Restore the iPod to factory defaults/new iPod.
If it still recurrs, then yu likely have a hardwre problem and return it to Apple for replacement.