Share your experience!
Ok, so my Xperia P was working fine until up to a few hours ago when it suddenly froze. Because this happens ocasionally I didn't think much of it and restarted (Power Button + Volume Up). When it restarted it seemed as if it had reset itself (there was a sound when I typed in the PIN code which I had disabled months ago, none of my apps on my homescreen were there...) but, strangely, my wallpaper that I had set was still OK. Suddenly, the message "Unfortunately, download music info has stopped" appeared and the phone and it then restarted. Again, the same thing occurred, and again and again... just continuosly restarting. Finally I pressed the power key and it gave me just two options (Power Off or Screenshot), so I powered off. I've tried switching it back on again, but the same thing keeps on happening. What should I do???
What if you repair the phone with PCC
Bridge (for Mac)
Alternatives on How to backup Xperias
http://talk.sonymobile.com/thread/36355
Hi BringMeTheOwls, welcome to the community!
Follow @Uliwooly's suggestion, here are some additional steps:
Running the software repair on PC Companion:
1. Install and open PC Companion then select Support Zone.
2. Phone Software Update.
3. Start.
4. Repair Phone
5. Continue
6. Accept data removal
7. Next
8. Wait for prepare
9. Select Phone
10. Follow the connection steps
Running the software repair on Bridge for Mac:
1. Launch Bridge for MAC without the handset connected.
2. On the Main Window select "Xperia > Repair Xperia
Device".
3. Ensure the phone is charged and select "Ok" in the
following window.
4. Select Continue on the following page.
5. Wait until the initialising step is finished the
continue as below.
6 . Select your model of phone from the list that appears
7. Follow the connection steps that appear, ensuring that
you are holding the relevant button down before during and
after the connection phase until the update/repair begins.
If this doesn't help then contact your local Sony Xperia Customer Care team like @Phy suggested 
I've tried the PC Companion option first but when I get to the stage where I have to plug in the USB into the computer and later, into the phone, holding down the Volume down key while I'm plugging it in and it's not working (the little light just turns green for a second and then turns red, returning to the charging screen).
I've tried holding the Power Key and Upper Volume key until it vibrates three times as instructed, but when I try the first instruction again it still doesn't work. The PC Companion still won't allow me to pass to the next stage.
Hi, this still doesn't work. Charged for two hours (was already at 100% when I plugged it in). Tried the Volume Down key procedure again, the light turns green, then red, then nothing while the word "Sony" appears on the screen... and then back to charging (it now says it's at about 90%, which is strange after charging for two hours straight!).