I assume your pc is fast enough to playback DivX? Cause if not it just cannot decode the sound + video fast enough what can cause into not matching sound.

First a question, is the sound to late?! Like a few secs or so?!
What you can do is rip the sound using Nandub (or VirtualDub) and make a version of the movie without sound aswell. Then rejoin the 2 just made files (audio and a videofile without sound) using the same prog and then you can select that you want to playback the sound a few secs later. You can set this in the audiosettings!