Out of curiosity, have you tried to render the video only to Mpeg2 and then the audio to AC-3 and use DVD Architect to make a DVD, and see if it is on sync.. Or even just render the video to Mpeg2 and the audio to AC-3 and then make a new project and drop them on the time lines and then render as normal. I know the quality will not be the same but it is just to try and work out what the problem is not.. rather than what the problem may be…