I just noticed that my iPhone 4s cutoff for no apparent reason. I used it an hour ago and it was fine. Now there is just a tiny asterisk looking dot in the middle of a black screen. I pugged it up to the computer and iTunes won't come up. I bought this phone on November 12, 2011 and it had all of the updates. I tried pressing the Power button but nothing happens. It is an iPhone 4s 16 gb black.