I can confirm that Dirac-into-Ogg encoding doesn't work at all with GStreamer as shipped in Ubuntu Intrepid, at least if the file also has an audio track.
As far as I can gather, it seems to be a bug in the version of oggmux used in Intrepid (gst-plugins-base 0.10.21). Strangely enough, Dirac-into-Matroska encoding works correctly in this version, whereas it was previously broken (hence why OggConvert normally won't let you do it).
I can confirm that Dirac-into-Ogg encoding doesn't work at all with GStreamer as shipped in Ubuntu Intrepid, at least if the file also has an audio track.
As far as I can gather, it seems to be a bug in the version of oggmux used in Intrepid (gst-plugins-base 0.10.21). Strangely enough, Dirac-into-Matroska encoding works correctly in this version, whereas it was previously broken (hence why OggConvert normally won't let you do it).