Hello, i have the same problem. I cannot load my back camera, sometimes the screen is frozen, sometimes is black and sometimes it closes from itself.
I tried with hard reset but i didn't help.
When i bought the phone it had Windows Phone 8.0 but later i updated it and now it has 8.1.
The main question is: Is software or hardware problem? What is the possibility of software problem?
If anyone have solution please contact me (toni_zver@hotmail.com)
Thank you.