After powering my iPhone 5 off then on I would get a black screen after the Apple logo. The only thing that is visible is the top line where the carrier logo, time and battery meter is and everything is black. Tapping on the screen or pressing any of the buttons doesn't do anything. I can still activate Siri or take a screen cap. I tried rebooting a few times and had the same issue. The only way I can get the slide to unlock screen to appear is to answer a call and hang up. It does not happen when I wake up phone and it is already powered on. I think narrowed down the cause. I have exchange mail for my work with a passcode. When I deleted the account and turned off the passcode, the iphone booted normally. I am not sure if this is a phone issue or iOS 6 issue. Is anyone with Exchange mail and passcode having this issue?