According to the guy I talked to last night, the issue is that there's some kind of field blending going on where, at some point, the two fields that are improperly interlaced are getting converted to progressive so that interlacing becomes part of each frame.
I guess what I need to do, after I try recapturing the DV stuff, is bring the stuff into a DV sequence and export it with de-interlaceing and some kind of plug-in to split the fields (which is what my guy told me but I didn't quite understand). Then I can bring it back into FCP.
Does that clear things up a bit or does it only make things more complicated?