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 END/Power key. To turn the device back on, press and hold the END/Power key until the screen lights up. Note: If you are unable to turn your device off, remove and re-insert the battery.
From the home screen, select Menu. Note: A Factory data reset will revert the device back 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.