I finally compiled ogg-support for Diablo too. It’s available through the maemo downloads page.
I don’t know why the Chinook version didn’t work in Diablo any more. And I didn’t really want to start debugging why the Maemo’s mime libraries and the closed source Metalayer Crawler don’t want to work with the mimetypes copied from a desktop system. So, now there’s only one mimetype: audio/x-vorbis and no support for speex or theora anymore. On the good side, e.g. File Manager can now start OGGs to Media Player.
New feature is a Control Panel plugin to ignore the OGGs from the Maps application. After installing ogg-support wait several minutes for the Metalayer Crawler to finish and then start the CP plugin. Metalayer Crawler seems to be much much slower if you have the Media Player open while it indexes the files.