That file is bizarre. It has all sorts of references to non-existent files, like "hildon-browser.desktop" and "hildon-mp_ui.desktop" and "hildon-image-viewer.desktop" When I replace the goofy associations with my preferred associations, (such as changing every line that starts with "video/" to "video/<xxx> = mplayer.desktop") and try to open the file from file manager, it doesn't seem to work, even after a reboot.