I tried to mirror my late 2011 iMac (fully updated running latest version of Mavericks) to my ATV to show the wife something I was looking at on the screen and the option has disappeared it seems. I've restarted both my iMac and ATV. I used to work but I can't pinpoint when the option stopped appearing as I don't use it very often. I recently updated Mavericks within the last few days (OSX informed my there was an update so I installed it). Is this a known issue?