I am not 100% certain that upgrading to ML is giving me issues with Apple TV playback (not mirroring) but I AM having trouble with playback of music and movie stored in iTunes/iMac mid-2010.
I have an iMac mid-2010, 3rd generation Apple TV, cable broadband connection, and linksys wireless router.
Ever since I upgraded my iMac from snow leopard to ML (and yes I followed all directions and updated my apple TV as well to the latest software version), Apple TV takes as long a 5 to 10 minutes to play a song in my iTunes/iMac.
I thought it was the broadband or wi-fi connection so I tried netflix streaming using apple TV and it was fine.
Playback of movies stored in iTune/iac are also affected and it takes a long time to load as well.
In addition, once the content is playing, there's lagging/buffering and the playback stalls.
What's going on? Is it the speed of the wi-fi or broadband as suggested by Apple troubleshooting tip and this forum? The only thing that has changed from the time that playback of itunes contents using apple TV was working vs. not is the upgrade to ML.
Anyone else experiencing this problem? Recommendations?