So appears to be a widespread (and growing) problem. For me, I logged out to test (thanks guys!
) and it won't log back in for imessage account only. For my MacBook which is old and stuck on Lion, it's similar to what happened for the beta earlier this week, which kept running fine well after the beta expiration on the14th, until I quit and re-launched it, which killed it. It could be related, maybe or maybe not. Is apple doing something to try and stop hackintoshes, maybe but I've heard that a 1000 times and 997 of them turned out to be untrue and the other ones eventually found a work around, so no need to panic. Yes many real macs have same problem and for a variety of reasons, but in comparison to how many real macs don't have this problem it's a small number, so if your real mac is fine and hack is not, don't expect that to automatically mean it only effects hacks, it's just that you weren't lucky enough to win the lottery. So to help in finding the cause, if you post and info is not in your sig, please make sure you include hardware info, OS version, relevant console logs you think may help, keychains (fyi, always take due precaution and be careful what you post) etc. I'll continue with some testing and digging around, but I'm only me and like many of us I already have more other things that need to be done between now and Christmas than will ever be possible.