You might try this:
You can restore the default factory settings for your device; from the Home screen, press the Center Select key for Menu > Settings & Tools > Phone Settings > Security > Reset Settings. Scroll up to select Yes and press the OK key. Your device will power-cycle and reset to default factory settings. Using the Reset Settings feature will not delete your personal information; it will restore only settings like default ringtone, keypad tones, and display settings.
Important! To access the Security submenu, you are prompted to enter your Lock Code. Your default code is set to the last four digits of your mobile phone number.