Some of my dvds won't recognize or play in my macbook. They just spin and stop, repeat a few times, and then eject from my macbook. No windows come up and the disc does not show up anywhere. These are store bought dvds that play fine in any other dvd player. For instance, the feature disc of "The Doors" won't play, but the special feature disc will. Some of my other dvds will recognize and play however. Please help.