I had this problem last night and like the other users in the BlackBerry support forum said, I rechecked if I was in an area with good network coverage and if the dates and time in my phone is current (answer: yes, they were). This is silly because if you're using BBM on iPhone like I do, there is no way your dates are going to be non-current as iPhone doesn't allow users to manually reset the time. What could have been be non-current in iPhone is your iOS 7. If you haven't already downloaded the latest iOS, do it, and then try to reconnect to your BBM. It should then work fine for you, no need to restart the phone or reinstall the program. Good luck! Now for this iOS update make sure you are connected to a good network because I heard if you disrupt the process then you will screw up big time because iPhone is not designed for third world countries where a good network can be considered a scarce commodity.