I usually don`t watch many movies/videos on my laptop, but I have been traveling a lot recently, so the X201 came in for that purpose.
While using it on the plane I have noticed that movies and videos in general stop/brake for few seconds when you incline the laptop, then as soon as the laptop is still again they resume, it feels like playing music on one of those old portable cd players that did not had ant-shock.
That's the ThinkVantage Active Protection System at work. It's a motion sensor and software which protects your hard drive from shocks. You should have a ThinkVantage Active Protection Control Panel which allows you to see it at work, and adjust its sensitivity.