Alright so, I jailbroke my iPhone 4 a few days ago. I was on my iPhone late last night and my iPhone didn't have this problem till I woke up this morning. At first I was like "What? Did someone come in and steal my sim?" Then I installed ultrasn0w and the No Sim problem went away. I live in the U.S. and I use at&t so... I just found that strange.