Try using the method wtitten in http://forums.afterdawn.com/thread_view.cfm/129217 . Or, if you just want to make an AVI, open VirtualDubMod, load that movie, add it the 'MP2 for SVCD' file you created with BeSweet (+ BeSweet GUI) substituting the old one (Stream__Stream list--> delete the old one, add the new one). Video__Direct stream copy and File___Save the AVI.
Yes, of course if the sound was already off-sync on the original movie the work you need to do is much harder, my method corrects the problem only if the out-of-sync feature comes when you convert an AVI to mpeg and the original AVI was in-sync...