When I enable airplay from my computer, my apple tv shows no video

Brand new 2012 Mac mini (10.8.2) and a 3rd generation Apple TV. When I play a video and enable "Airplay" the sound is played through the Apple TV, but the video appears on my computer.

I have tried this with Quicktime Player, VLC, Safari playing YoutTube videos, Movist,

I can send airplay video and audio from my ipad and iphone.