Audio problem: When Arwen and Aragorn are talking on the bridge, you see Arwen's lips moving while Aragorn is speaking. When you zoom in you can see that Arwen's mouth is definitely moving as she is talking animatedly, both when neither character has any dialogue and when Aragorn's voice says 'I thought I had strayed into a dream'. (01:32:15)
Audio problem: When Merry, Pippin and Frodo are separated by the Troll's club smashing the ground beneath them in Balin's tomb (right before Frodo gets smelled round the pillar), Aragorn shouts, 'Frodo!', but his mouth is not in sync (it looks as if he shouts 'Legolas' in that shot, but it was dubbed over.) (00:30:00)
Audio problem: In two shots at the end of Frodo and Gandalf's conversation in Moria (before the Fellowship enters Balin's tomb), Gandalf's beard is moving as if he were talking, but he doesn't say anything.
Audio problem: When Bilbo and Frodo are reunited at Rivendell, Bilbo embraces Frodo and Bilbo's voice can be heard saying "Oh." But, his mouth is closed and could not have possibly said it.
Audio problem: When Haldir is seen talking to the Fellowship in Lothlorien in the extended edition, he says "You can go no further." From Aragorn's point of view you can see Haldir saying "You can go no-" but when Haldir is walking away, he isn't moving his mouth to say the word "further." (00:46:18)
Audio problem: When Bilbo is saying good-bye to Gandalf outside, he's standing by the door and then he turns to walk to his gate. When the camera angles behind Gandalf, Bilbo is standing at the gate with it open; the gate is too far away for Bilbo to have been there in a split second, and we never hear the gate open, but we hear it squeak shut. (00:29:15)
Audio problem: At Orthanc, as Saruman and Gandalf walk towards the Palantir, Saruman asks, "Why? Why should we fear to use it?" but his lips say something completely different. (00:48:40)
Answer: "Fly, you fools"