Perform a soft, factory, and alternate master reset of the device.
INSTRUCTIONS & INFO
There are multiple ways to reset your device if you are experiencing issues. The first step is to power cycle your device. Press and hold the Power button. To turn the device back on, press and hold the Power button until the screen lights up. Note: If you are unable to turn your device off, remove and re-insert the battery.
If a restart does not resolve your issue, you may need to perform a Factory data reset (Master reset). This will erase all data on your device and restore it to factory settings.  It will permanently erase all personal data, preferences, settings and content such as pictures, ringtones and apps that are saved to the device. It is recommended that you save (backup) important data before proceeding. To ‘Factory data reset’ your device, from the home screen, select Menu.