iTunes won't let me download movie, says I don't have enough local storage, but I have 3.5GB...

So I'm trying to buy and download the movie Resident Evil. I click buy movie and a message pops up saying that I don't have enough local storage space to download the movie. I have over a GB at this point, but I deleted some things that could be easily removed or re-downloaded later. I now have over 3.5GB of local storage space. However, I'm still getting the same message, which makes no sense. Why on earth would it take 3+ GB to download a single movie??