We were trying to create DVDs with the workflow Avid Xpress Pro -> (export Quicktime ref) -> Sorensen -> (convert to MPEG-2 DVD Pal) -> DVD Flick.
The output from Sorensen seemed okay when played locally, but the DVDs produced by DVD Flick had audio slightly earlier than video. After a long time searching, we stumbled upon a forum post where a guy (thank you, "dng"!) in a similar situation had resolved the problem in DVD Flick by going to Edit title... -> Audio track -> Edit -> Ignore audio delay. This worked perfectly for us, and showed that the audio delay in the MPEG from Sorensen was -160ms or so, which explains why the audio was slightly ahead of the video. Perhaps the media players we used (Quicktime and Windows Media Player) ignored this metadata which was why it seemed fine until burned as a DVD-video?