I found out that deleting ~/.local/share/applications/transmission-gtk-usercustom.desktop fixes the problem for me.
-- Transmission doesn't open torrents via Firefox 3 https://bugs.launchpad.net/bugs/204184 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs