Fields Vs Progressiv

So in the past I have put together tapes using our blackmagic card where I first rendered the project from AE as a 720x540 progressive frame animation. I let FCP re-size it to 720x486, and use lower fields in the sequence settings to write to tape. This always looks much better than sending things over to tape via progressive scan. As of late I have been having a problem where by the frames coming through the Black Magic card and going to tape end up having half of the first frame, and half of the second frame as one frame. Generally its the top of one frame and the bottom of another, and not just fields as they should be. If I change the sequence to no fields, my curves and angles dont look as crisp, but I dont end up with the same problem. Can someone shed some light on this for me?
-A

So, sorry for the double post.. some kind of safari hang up.. Anyhow.. I should also mention that I got the same problem when I rendered without fields. Any clues?

Without actually doing the math (it makes my head hurt) it sounds like the dance that happens during 3:2 pulldown. Are you creating the graphics and importing them at the same speed? Is the timeline at a matching speed?

If you create graphics at 24 and import them at 30, you get one, one and a half, one half and one, one, one, etc. etc.

Koz

I cut stuff and it goes into after effects using de interlace setting, put it back into FCP and edit to tape via decklink. If there are problems I use FCP's video filters and it cleans up flicker, motion blur and looks very good. I don't know if this is any use but check it out.