can't fix field order in FCP for mpeg export

I'm on a nightmare project... or at least it's turning into one. And I desperately need help!

I have media (quicktime, lower field first, exported from an Avid MC - one of those really old ones that still run on Mac) in my timeline, which I need to cut new graphics into. There are over 50 titles, some with up to 5 layers of moving text, which then need to be translated into 9 different languages. Deadline was 2 weeks ago, of course.

the project: I finished my 8 English timelines, with titles, then duplicated those timelines and replaced the text with the next language. After initially creating titles in photoshop, I then choose to re-do them in FCP - because the deadline was looming and they actually looked nicer. Each title has 4 layers; 2 layers move on and off with an Edge Wipe, the other 2 move on and off/resize using the Motion settings. Not the best but it needed to be quick and easy to replace.

the problem: when I export (to mpeg2) from the original English timelines, the video is jittery (like the field order is wrong), but the titles look smooth. The duplicated timelines in the 2nd language are the opposite - smooth video, jittery titles.

I have tried: changing the timeline settings from lower to upper and even de-interlaced. Deleting all my renders and re-rendering. Exporting straight to Compressor using default compressor settings (DVD mpeg2 best quality 120min - field order automatic). Exporting a quicktime reference (current settings, not self-contained), then compressing this. Copying the compressor settings and forcing it to 'lower field first' (on the timeline rendered as lower first). Obviously burning the mpegs to a disc to check on a monitor each time.

I am at a loss as to what to do next. please someone tell me I have overlooked something stupidly obvious. any suggestions would be muchly appreciated!

2.5GHz PowerPC G5 | Mac OS X (10.3.9) | 4.5Gb DDR SDRAM

Final Cut Pro HD 4.5 | DVD Studio Pro 3.0.2 | Compressor 1.2.1

Adobe Photoshop CS | Adobe After Effects 6.5

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Mac Pro: Two 2.66 GHz Dual-Core Intel Xeon | 4GB RAM | ATI Radeon X1900 XT 512MB (2 x dual-link DVI)

Studio 2 | Adobe Photoshop CS | Adobe After Effects 6.5