OK ... well, I have re-built my ATV1 removed all media re-configured, ensured that my iTunes download option is set to 720p, but still no joy. This issue is not about what will, or will not play on my apple TV. The issue is this : there is some content - movies - that will not 'sync' from my iTunes Library to my Apple TV.
I use an external drive 500GB managed by FireCore.
During my 'rebuild' process I changed from external to internal storage, but still a number of my film media files will not sync.
My iTunes 'Movie Library' contains 102 items
My Apple TV 'Movies Listing' contains 86 items
Some of my movie collection on the ATV1 (historical) is at resolution 1080p - and plays(courtesy of FireCore). So it cannot be argued that the resolution prevents sync'ing from iTunes to ATV1, as this data has sync'd both previously, and over the past couple of days.
The films were purchased from iTunes, and the info clearly shows the download/purchase date and account (mine).
One of the films that steadfastly refuses to sync to ATV is currently syncing to my iPhone4