Just got an Xperia S and tried to upgrade it. I followed the instructions, but the phone was automatically shut down during the process of upgrading (while downloading software). It happened a few times and every time my phone had at least 70% of power to begin with. It's very frustrating and I had to give up upgrading. I'll really appreciate your help and any suggestions.
Its the same thing happened to me today .. and my cell was not starting at all.. not have to take it to sony service center.
I had the same problem. Don't connect your phone to the system using a USB hub or a USB extendor. Connect it directly to the USB port of the system. A hi-speed port is preferable (at the back of the CPU). Or try connecting to other ports.