Try performing a system repair as this will often fix issues - This will factory reset your phone, If that fails then either return your device to the place of purchase or contact Xperia care to have you device inspected http://www.sonymobile.com/global-en/support/contact-us/
Switch off your phone and unplug from Pc (Hold volume up and power for around 10 seconds) Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the onscreen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process
If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP
