Glitch during movies?

I have 5 purchased movies from iTunes and when I try watching them, they glitch. The glitch happens in the first 5 minutes and it simply stops the movie screen on whatever scene it's on, then speeds through the next 30 seconds before continuing on. This happens every 3-5 minutes during a movie, totaling up to 30-40 glitches per movie. It's very annoying and I just want to watch my movies! Thanks for any help.