Wait wait, I’m not really sure there is a problem here because:
Quicktime (when set to High Quality) shows the interlace lines even when the field order is correct. So seeing a comb effect is not a bad thing, as quicktime just shows you the fields.
So that said:
Does your movie stutter? Feeling it’s jumping back and forward? That would indicate a field order problem. Though i’m not even sure that quicktime can show a field order problem on a LCD screen.
A smart trick to check this in FCP: Take a bit on the time line, and reduce speed to 50% with frame blending on. Now go frame by frame through the clip. If you see the jumping back and forward effect, the field order is wrong. If it just goes slower the field order is correct.
Last, if you want to deliver a smooth quicktime without interlace lines, you DO have to de-interlace the movie.