Android: Uninstall and reinstall Viber
1. Enter into your Android's system settings (on most models this can be done by selecting the device's menu)
You will then see the device settings menu:
Select the 'Settings' tab.
2. Select 'Applications' -> 'Manage applications'.
3. Scroll down until you see the Viber application and select it.
4. Click "uninstall".
5. Download Viber from http://www.viber.com and install it.
6. After re-installing, set Viber up again.
Note that you can use the same access code as before, or receive a new one by registering your number again.
Please note that uninstalling the Viber application will also remove your message history.