Apple TV 3 Gen Update 5.1
iPhone 5 iOS6
iPad 2 iOS6
MacBook Pro 2011 OSx 10.8.2
Since the Apple TV update yesterday I was dealing with the same problems. I always had my Apple TV hooked up with ethernet and it worked just fine. Now with the Apple TV update and iOS6 had Airplay Youtube & Video and Photostream issues.
I did some test today with unplugging the ethernet and used my wi-fi cnnection and everything worked excellent. Netflix, Trailers, Youtube and Yotube Airplay using the Jasmine App, Trailers, Airplay with Real Racing 2 HD, actually worked better than it has before I did the update.
I still don't understand why ethernet to Apple TV is an issue, but Apple definitely needs to fix that. But I have to say they made great improvements on the wi-fi with Apple TV.
One tip for anyone having issue with Video AirPlay. I tryed playing actual recorded video from my iPhone 5 and tryed airplaying from my iPhone to Apple TV same issues as everyone else is having wouldnt play on Apple TV saw streaming circle just keep spinning and the video woudn't play on Apple TV.
Here is what I did to get the videos to play:
I tranfered the recorded video from my iPhone to my MacBook Pro and then imported the videos into iTunes and drop and dragged them back onto my iPhone and iPad. The videos will show up in your Video App and from there they will AirPlay no problem.
For some reason videos that we record on are iPhones and iPads show up as videos in are photos app and if you try to airplay them from the photos app they will just hang. But if they are transfers to the Video app via iTunes they will Airplay no problem.
Again another issue that needs to be addressed by Apple.
I hope this help out with the issues in this forum.