I upgraded Apple TV late last week. Last weekend I rented a couple of movies from Apple TV. I watched one immediately, and was going to watch the other one the next day. On Sunday I opened up Apple TV to watch the film, and..... NOTHING THERE. I could see 'purchased movies', 'top movies', etc., at the top of the bar, but no mention of rentals. Even the film I'd watched (which obviously you can see for 48 hours) had disappeared into a black hole in Apple TV. I have been charged for these movie, and sent in a complaint.
My airplay seemed to be fine, but.... last night, my computer was not seeing an Apple TV or showing an airplay sing, so I restarted and the Apple TV and airplay sign returned. If I chose to watch the film on the computer it started up immediately, if I chose airplay, I got the first image of the film and the loading sign going on and on (round and round) forever. The film never started. I restarted my Apple TV, the same. I restarted the computer, the same. I tried with various programmes and no go.
iMore has the following suggestion. I am not sure if this will help. It sounds a PIA, but if I can't get airplay to work, I might try it: http://www.imore.com/how-restore-2nd-or-3rd-generation-apple-tv-back-factory-set tings-itunes