Phone was working fine until I downloaded the latest software update which supposedly fixed the proximity issue. Now my phone will not connect to my wifi connection. It had been doing, and working perfectly, now when I try to turn on wifi it just says error underneath it. It has also led to the phone turning itself off randomly with no rhyme or reason behind it. Can anyone give me any clues as to what's happened and what I can do to fix it? I've tried a factory reset several times. Once whilst the phone was on and several times whilst it's off.

Any ideas?