having same problem on both a MacBook Air HS + MacBook Air S but iMessage and FaceTime working on my iPhone without issue.....I tried everything, was on with apple senior rep today but had to go so will call tomm and report back if any new info....it has to be on server side as I can sign into everything else, who knows!Is there any further update to this issue? I am now getting the same issue, Messages asking for my password repeatedly, and I did everything that was discussed previously.