Can't log in to Messages and FaceTime

My Messages and FaceTime apps broke on my iMac. Neither accepts my Apple ID password anymore, despite the password still being used successfully for iTunes, etc. (My MacBook pro, which I didn't update has no issues and my iPads and iPhone are fine too.)



I've reinstalled OS X but the problem persists.

via ehMac.ca http://ift.tt/1qUXWZU