I have an iPhone 4 with the most recent version of the software. For the second time in about 5 weeks, my phone app has completely stopped working and only shows a white screen when entering. I can still receive calls however. The only way I could fix it before was a complete system restore, which was horrible. My battery drains really quickly and the iphone gets really hot. The system restore seemed to fix it for a few weeks last time. I tried hard resets, soft resets, and everything in between. A friend of mine had the same issue with his phone.