I'm not certain but try booting the phone from the Internal low level recovery.

1. Turn it off

2. Once off, Hold down a combination of buttons, hold and press Volume Up + Volume Down + Power button until you see a Boot recovery menu. You will notice that your Notification light will turn PINK or RED

If that doesn't work try Holding volume up + power button simultaneously or Volume down + Power button simultaneously.

Use Volume up or down to make a selection within the menu, scroll to something that says """"""" Wipe Partition/Factory Reset""""" then Tap the power button to confirm your selection.

Do not click anything else but that, you can brick your phone!! Once it boots you have a fresh device :)

If you need a Reference, Here is a site that will help:

http://www.theandroidsoul.com/boot-sony-...

Update me if this helps you, Keep me tabbed :)