Other mistake: When the stormtroopers break into the control room, the stormtrooper on the right of the screen hits his head on the door frame. On the DVD release they've added a thump when he hits it. (01:18:55)
Other mistake: When Bilbo is looking at Thror's Map, he says "This hand points from these runes," but there are no runes visible where the hand is. Later, Elrond reads the Moon Letters that appear there, and says that they say, "Stand by the grey stone when the Thrush knocks, and the last light of the setting sun will shine upon the keyhole." But the Moon Letters actually translate to "Five feet high the door and three may walk abreast."