Anyone having issues with iMessage? Multiple conversations today would abruptly stop saying "delivered" and just say nothing. 5 minutes later it would send the messages as texts. I thought maybe it was because they were on Verizon and received a phone call etc, but it has been happening a lot. Tonight I tested it with a friend who is on AT&T with full bars while sitting next to me. Lots of the messages failed to send over iMessage, and were instead, sent in the green text bubble. Anyone having this issue or know of a way to fix it?