Since upgrading shared-mime-info to 0.40, all files are recognized as application/octet-stream under GNOME 2.22 on Mandriva Cooker. Reverting to 0.30 makes it work again. Here's an example:

[goetz@n5 ~]$ gvfs-info file:///home/goetz/tiny.mp3|
display name: tiny.mp3
edit name: tiny.mp3
name: tiny.mp3
type: regular
size: 2048
attributes:
  standard::name: tiny.mp3
  standard::type: 1
  standard::size: 2048
  standard::display-name: tiny.mp3
  standard::edit-name: tiny.mp3
  standard::copy-name: tiny.mp3
  standard::content-type: application/octet-stream
  standard::icon: GThemedIcon:0x8053980
  standard::fast-content-type: application/octet-stream
  unix::device: 839
  unix::inode: 1918371
  unix::mode: 33188
  unix::nlink: 1
  unix::uid: 709
  unix::gid: 100
  unix::rdev: 0
  unix::block-size: 4096
  unix::blocks: 8
  time::modified: 1193140977
  time::modified-usec: 0
  time::access: 1213344306
  time::access-usec: 0
  time::changed: 1193140977
  time::changed-usec: 0
  etag::value: 1193140977:0
  id::file: l839:1918371
  id::filesystem: l839
  owner::user: goetz
  owner::user-real: Goetz Waschk
  owner::group: users
  access::can-read: TRUE
  access::can-write: TRUE
  access::can-execute: FALSE
  access::can-rename: TRUE
  access::can-delete: TRUE
  access::can-trash: TRUE