I am having the same problem, and it seems Apple doesn't even know how to fix this issue.
I am trying to download a rental movie like i always have into my appletv. I have tried restarting the AppleTv, restaring internet connection, etc etc. Nothing seems to work. I have even read that reseting the AppleTV doesnt even work.
PS: Please dont tell me to check some temp folder because im not using a computer. This whole operation is on the appleTV.