Hi. I upgraded my iPhone 4 to iOS 5 from the latest iOS 4 version, Everything seems to be working fine except iMessage. It will not work, no matter how hard I try. Whenever I send an iMessage, it says delivery failed after a long while. If I tap the exclamation mark next to the bubble and select the try again option, I get no progress bar unless I go back to home, lock the phone, unlock and open Messaging again. The progress bar then shows and remains stuck at 90% for a long while before failing again. This happens again and again, no matter how many times I retry. I cannot receive any iMessages either. Every other method is working fine, including tweets, emails and text messages. If I add my own phone number as a contact and send an iMessage, it goes through and shows up in as received too almost instantly. I have tried with 2 different people for whom it works perfectly when they send iMessages to each other, I have confirmed all settings and methods to be identical. I have confirmed that activation is successful and have reconfirmed my Apple ID and have viewed all details within the configuration options located in the Settings > Messages menu. I have tried over Edge, 3G and Wifi. I have restarted Messaging many times along with turning the iMessages option on and off multiple times. I have tried rebooting the phone and turning iMessages off before and on after and leaving it on during the reboot. I have also tried a factory restore with and without reinstalling my apps on it. Nothing fixes the problem and I am very frustrated. How can I fix it? Please help.