I can’t really visualize the artifacting you’ve described in your post.
Have you tagged the pixel aspect ration of your DV footage to D1/DV NTSC Widescreen (1.2)? Is your widescreen comp 720×480 with a 1.2 pixel aspect ratio? Are you using the Pixel Aspect Ratio Correction button on the composition window to visually stretch that to appear 16×9? That might be creating the visual artifacts you’re seeing. I usually bring anamorphic NTSC video into an 864×486 or 864×480 square pixel comp and then stretch that back to 720×480 in the output module.
Shawn Marshall
Marshall Arts Motion Graphics