Audio problem: During Marge and Homer's argument at the beginning, when Homer says that Ned Flanders is a jerk, his mouth doesn't match what he's saying. (00:01:55)
Audio problem: When Ned calls Homer and says "over here" his mouth doesn't move. (00:17:30)
Answer: I'm not sure if this is the one you're thinking of, but an episode of "Ray Bradbury Theatre," called "A Sound of Thunder," dealt with a similar matter: a group of hunters travel back in time to hunt dinosaurs, only to find things have changed when they get back because someone stepped on a butterfly.
Xofer