Your source was probably shot in 2:1, now you've got an unsupported size. 'I suppose FCP doesn't like DVCProHD in any other size than 720 or 1080. You can crop or letterbox you footage in RR to get one of those size in 16:9.
But I suggest Clipfinder for transcoding, it' miles ahead of RR by now (and free as well).
Hope this helps,
Director of the Institute of Media Research (IMF) at Braunschweig University of Arts