I have bought a A5 as a present for my wife lately. Its touch screen has already frozen two times. In the first case, somebody called her, and when she took the phone out of her pocket, she couldn't answer the call because the touch screen didn't work. She tried to restart the phone and kept pressing the on/off button. The menu correctly came up, but she couldn''t restart because the her touches on the "restart" has been ignored. In the end she had to remove the battery to restart the phone. The second case was this morning. The alarm went off, but she simply couldn't switch it off because of the unresponsive touch screen. I had to wake up and take the battery out again.
I am not sure if it is related, but in both cases the screen has touched something when the phone started working. First the material of her pocket, and in the second case the phone was laid down on the carpet, facing down.
Please help, because it is so embarassing to give a present which is not working well...