Make sure your internet connection and access points are fine and try again.
2013-02-11 16:31 - edited 2013-02-12 13:36
Try the following troubleshooting steps:
1. Restore factory settings
Go to Settings>General>Factory Settings. The default code is 12345 unless you have changed it. It will restore the phone back to its original settings without affecting your personal data such as contacts and messages
2. Update or Reinstall Software
Download Nokia Suite. Connect your phone either via cable. Under updates section, it would notify you if an update is available. If none, click on "reinstall" to reinstall the software.