I think I may have found a bug in iTunes purchases.
I purchase a moviw in iTunes, purchases have been made on both iPad and on iMac.
Movie will not sync to Apple TV
Error message from iTunes "video format not supported by Apple TV"
Copy movie to another location
Delete movie from iTune
Add movie to itunes manually - drag drop onto itunes.
Movie syncs and plays on Apple TV
Just though I would share in case anyone else was experiencing the problem.
I noted another sympton, the newly download movie does not show any artwork and is missing some meta data. When is is improted for the second time manually artwork and al meta-data appear as they should.
This has happened to every movie download since installing 10.8. The work around is easy but this is definately a bug.