I'm using Adobe CC 7.0.2, iMac 27" 3.2ghz, OSX 10.8.4, and have a second screen attached through the Thunderbolt/DVI adapter.
Up until about a week or so ago I was able to play output full screen to it and still edit on my 1st screen (Mac) - but even if i have Screen 1 or 2 selected, it won't playout to either of them. I don't use Matrox or any external devices, and it's frustrating as I don't believe I've changed anything since. I have Enable Transmit on in the Program window too.
Maybe I'm the only one with the issue - it's annoying to not be able to use it.
I hope this gets resolved as I'm considering the same setup.
I don't know what it is - I have Enable Transmit on the Program monitor to enable it to do so, and I can't go back to 7.0 or 6.0 as I'm now working on projects in 7.0.1 and don't want to keep chopping and changing.