well.....after working on over 1000+ iphones, i think one of the most important step is to reset the device after a hardware or sotware update

the iphone is preety much a computer in your palm,just like a computer, if the iphone hangs or acts weird the first step is to manually reset the device

here what to do......

1) make sure device is charged, or sitting on charge

2) power on the device (if device is on, skip this step)

3)press and hold both the home button and power key for 15-20 seconds

4)once the screen blanks out, press the power on key for 2 seconds

and woo-hoo here comes the apple logo, if problem still persists restore it !

this guy knows iphones better than apple.