hey Nat,
What program is telling you it is interlaced?
If it is FCP, ive noticed that sometimes if the settings match what it thinks “should be” an interlaced comp, it will set it to be, even if it isn’t.
You can manually turn off the field dominance in FCP, and if it is a True 1080p, you will get the full resolution.
If you are getting field lines in QT or something, that’s a whole other problem, but don’t ever trust what FCP “thinks” your comp is, it is wrong…a lot…trust your eyes :).
-Dan