Last night I was using my iPhone fine and with no problems. I turned it off before I went to bed, and then when I woke up this morning, I turned it on. After a few moments, the screen displayed for me to plug my iPhone into iTunes and I could make an emergency call if I needed to. So I plugged it into iTunes and when it appeared in iTunes, a message came onto my phone that said "iPhone is activated". I have no idea why it would prompt me to do this. I have had my iPhone since the day it came out in July of this year without any problems (like this not happening) and it is not jailbroken/unlocked.