sound out of phase with video...

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I have been encoding my DVDs as divx and every single one of them has the same problem, wether its encoded as divx 3.11 or 4. Watching the movie all the way through is fine, But when i skip, through the movie, where it starts again the sound is lagging about 3-5 seconds behind the video. Ive tried increasing the keyframes to 1 every 18 frames but its still lagging about 2-3 seconds. Any suggestions on how to fix this??