I fixed this in Ubuntu with this edit (we're still using the desktop-file-utils package to set default mimetypes)
http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/oneiric/desktop-file-utils/oneiric/revision/43 -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
