There are Mac Mini 2012 with OS X 10.8.2 and Apple TV 3rd G with 5.2 (6010.96). There are 2 users on the Mac.
The problem is when I start Mac Mini and log on with one user I am able to mirror the desktop. When I switch to another user and try to mirrow the desktop, I see bad image (image full of green artifacts) with good sound.
One user is admin. It does not matter which user is sharing the screen first. It is always the second one that will not be able to mirror the screen till Mac Mini is rebooted.
At the same time if I try to airplay something from iPhone or iPad, it goes well.