Have you found a way to resolve this problem? I’m having the same exact issue.
Here’s my screenshot from CatDV (9.0.6):

This is what it looks like in FCP7:

And when I scale it down to 75percent, you can see it looks strangely wide, letterboxing inside the 16:9 canvas. As if the pixel aspect ratio is not registering or something:

Any info or suggestions would be greatly appreciated!
Thanks,
Jack