Episode 3 of a purchased TV show takes 4 hours to download, so cannot watch it. What is the problem and how can it be fixed?

Through iTunes, I purchased Season 2 of Downton Abbey, which is a Masterpiece Theater series. I watched Episode 1 and 2 without a problem, but when I try to watch Episode 3, it says it is loading, and then says it will take 3, 4 or 5 hours to download. I have tried going through iTunes troubleshooting, but with no success. Any ideas???