'This movie requires QuickTime, which is not supported by this version of iTunes.'
Try relaunching iTunes in 32-bit mode first, as per the instructions in the following document:
Can you watch the movies and TV shows now?
I've rented and bought movies through the AppleTV and played old movies from my library no problem. But for some reason, when I tried to rent Little Miss Sunshine and buy a season pass for Homeland through iTunes on my computer, I get the error message. The last I heard from Apple they were investigating the movie, but I haven't heard anything else since. I'm flummoxed. But I will be making an appointment with the Apple Store.
I am having this issue all of a sudden as well. All of my movies that were purchased out side of iTunes have no problems, but I just purchased The Hunger Games and Battleship and I have tried to download some old series I previously purchased and they tell me that quicktime is not supported in this version of iTunes. They really need to fix this.