I've found since I upgraded to Mountain Lion on my late 2009 white Unibody MacBook, Airplay has not worked well. iTunes sees the ATV, and the ATV sees my music library. But it pauses all the time. Sometimes before it even starts playing, and almost always a few seconds before the end of a track. By "pauses" I don't mean stuttering or dropouts. I mean that the iTunes button literally goes from "play" to "pause" on my MacBook. AirPlay works just fine on this AppleTV from my fiancee's late-2007 MacBook running Lion (don't know if latest version), and also from both of our iPhone 4S's. Just not from my MacBook, which is of course the source we usually want to use, because it holds my music library including all of my digitized vinyl. It doesn't matter if I initiate play in iTunes on the MacBook, or on the ATV3. (As I wrote, it sees my library just fine.) Any ideas how to fix it? Here's the complete setup: Late 2009 MacBook (white unibody), 750GB HDD, 8GB RAM OSX Mountain Lion 10.8.1 iTunes 10.6.3 <wireless> Apple Time Capsule wireless router (don't know firmware version) <wireless> AppleTV3 with 5.0.2 (4250) software, connected via HDMI to an Anthem MRX 300 A/V receiver.