Thanks, I'll give that a go.
But in the mean time, I've exported in Lagarith, and I end up with junk frames (same with HuffYUV). Not only that, but the playback is erratic, and cuts out just before the end of the clip. Despite all this, I tried to encode in Zarx264, and I end up with the error:
CAVIStreamSynth: System exception - Access Violation at 0x0, reading from 0x0
What's all this about?