Yeah I'm getting that now as well.
Earlier it was showing me my purchased films and rentals and was letting me play them when using US.
However now they arent showing at all under US and I cant purchase anything either.
Set it back to UK and still no Movies.
However my other ATV has just done a software update and after resetting it does have movies on it (no TV Shows though).
So i'm going to bite the bullet and do a factory restore on my ATV in the off chance that this gets movies back (not holding up much hope though).
Havent been able to get hold of Apple Tech support yet - so still not sure if they are aware of this problem or working on it... I would hope they are - but their system status page still shows everything as being ok: http://www.apple.com/uk/support/systemstatus/
I havent yet seen any posts from anyone else yet stating that they've spoken to Apple about this... Is anyone logging this problem with their Tech Support?