Does the offending clip have any stills? Rule of thumb is that you should always de-interlace. Stills may make it through all the proofing stages OK; but freeze after they are authored. Another suggestion is to follow Ken Stone's method of creating a disk immage prior to burning
http://www.kenstone.net/fcp_homepage/image_to_disk_stone.html; as this will give you a true DVD; not a simulation, and thus a more representative proof of the file.
Best,
Al Davis
Visual Velocity