Apple TV loses movies after syncing from iTunes

Question

I'd be grateful for any help I can get on this: I bought ATV a few weeks ago and have a movie on iTunes on my iMac that I want to sync to ATV. I click on the sync button, and the sync process starts.....and the sync process finishes.....perfect, you'd think. It appears on ATV under "My Movies" with not problems. And then I shut down iTunes on my computer, at which point the movie disappears from the "My Movies" section in ATV.
Looking more closely, it's clear on the bar in the sync window that the data hasn't copied across because the amount of data on the ATV relating to movies should have doubled, when it hasn't increased at all!
I've repeated this process 3 or 4 times - no luck. Movies bought from the iTunes store via the ATV sync to the computer perfectly.
My wireless network is via a time capsule set to N rather than B or G - does that affect anything?
Please can anyone help before my wife files for divorce? I'm beginning to think that the ATV might just prove to be one "little white box" too many for continued marital harmony!
Thanks.

Answer 1

OK I've done a LOAD more work on this and I think it's related to the port 3689 thing so many people are having problems with.
Photos and music sync fine. I don't have trouble finding ATV in the devices from iTunes. But still, every time I try to sync a movie from iTunes to ATV, it goes through the process with no substantive outcome. When I shut down the mac or just quit iTunes ATV has no movies.
One of the movies I'm trying to sync to ATV was one originally bought from the iTunes store via the ATV, so I am certain there are no movie compatibility issues.
I tried to do a custom sync also - which achieved nothing except to generate the port 3689 error. I can get rid of the 3689 error message by turning off the firewall - but that's not such a great achievement given that it still simply goes through this phantom sync process with no eventual outcome.
As I said, maddeningly, photos and music sync perfectly - the rainbow bar on the sync page almost instantly demonstrates new content on the ATV as soon as the process starts. It never does this when syncing a movie.
So. What now? At the moment I have an expensive white and grey brick and I am very very unhappy. I would take the whole lot back to the shop if it weren't for the "told you it was a waste of money" look I'll get from the wife!
For background, it's a wireless network running off a time capsule with one airport express as a bridge. No windows or pc rubbish in the house!
Does anyone from Apple read these posts? If so, what is being done to fix the problem - or are we all to be compensated appropriately for the time, effory and money spent?
Thanks.
Graeme.