I've been unable to use my Macbook Air with an external monitor for the last couple of weeks because the Air's own display doesn't go to sleep anymore when plugging in the external display. I can't use the computer like this because windows open and distribute over the Air display (which is closed) and the external display in random fashion. I use a TB display at home and a HP 30"er at work. The issue is identical with both displays. I never had this problem until a few weeks ago. I've searched various forums and posted on here and nobody else seems to have the same issue. Should I give up and send the Air in for repairs, or is there anything else I can try? This is incredibly frustrating and I can't really be without the Air for a week.