I have a 2012 MacBook Air, Mountain Lion, and an Apple TV 3. They're all connected wirelessly through a Time Capsule. I tried out AirPlay Mirroring today, and ran into a problem. When I chose the Apple TV from the list to AirPlay to it will briefly change the resolution on my Air, flash on the tv, then return to the regular screen without being mirrored. If I try it again, it will start displaying on my tv, but has black bars all around the screen, and the settings on the Air under Display Preferences says AirPlay mirroring is Off. I try to select the Apple TV, but it won't stay selected. The additional settings for resolution and overscan briefly flash, then disappear. Of course I tried resetting my computer, resetting the Apple TV, restoring the Apple TV, and going through all the settings on the Apple TV to see if changing any of them helped. Nothing did. I tried searching, and while I found a lot of other problems with AirPlay on Mountain Lion, I didn't find this one. Any other ideas to try and get it working? I guess the next step is trying to reinstall Mountain Lion. Edit: I finally got it working by using wired instead of wireless on the Apple TV, and turning the wifi off then back on on the Air. I can't imagine why that did it when all the power cycles in the world didn't work. But I'm still running into some of the other issues that I read about when trying to find a solution to my problem. And after disconnecting it won't work again.