I had the same problem and I solved it applying to the video asset the “Revert to Original” instruction. Surprisingly it worked and I built the DVD correctly. I noticed that the video asset was reinterpreted as 1.066 aspect ratio video, been originally a 16:9 clip (1.422), but when putted in a 16:9 timeline it was shown in its correct pixel proportion.
All the pixel aspect ratios mentioned above were used in a PAL project.
Hope It´ll be of any help.