Jumpy Movies and playback

Have you heard of this?
In Motion 3.0.2 a simple still over black sliding across the screen looks jumpy when playing inside Motion and then when that timeline is exported as a QT movie and is dropped inside FCP timeline, (but smooth playing out through its Kona or IO.)
The project is SD. I've exported as animation, DV and Uncompressed 10bit all with the same results.
If I play the movie exported from Motion in Quicktime Player it looks jumpy. Going slowly it appears all the frames are there, but QT can't seem to play the movie smoothly.
So if I make an H264 movie for the web it too looks jumpy. Looking at that H264 movie on a PC shows what looks like a field order problem of some sort with blocks of horizontal lines kinda shifted left or right of where they're supposed to be.
Any ideas what might be causing this and how to fix it?

I've had the same results playing this file on the machine it was created on= MacIntel 2x3 GHz Quad-Core Xeon 2008 running Tiger 10.4.11, Motion 3.0.2, FCP 6.0.4, and QT Players 7.2 and 7.5 (don't know why both versions are available), 16-bay SAN
And also playing this file on a MacBookPro 2.6GHz Intel Core 2 Duo, running Leopard 10.5.7, and QT Player 7.6.2, Motion 3.0.2, eSATA 2-Drive RAID and FW800 SATA external drive.