A factory reset can often fix many types of software performance issues such as battery issues, freezing and other software glitches.
Please be aware that this process will erase any user data and applications currently stored on the unit, so ensure important files are backed up first.
The following link contains instructions on how to perform a factory reset on your iOS device:
http://support.apple.com/kb/ht1414
Please ensure that you are restoring to factory settings, and not reverting to a backup.
If you continue to have any issues, please feel free to contact our Support Team for further assistance.