After the latest Gnome component update, default associations of Gnome apps with various filetypes have vanished. File-roller, for instance, is no longer associated by default with archives; for filetypes that would normally be opened with it, I have to specify that they be opened with file-roller, or I get a "Couldn't display [file]" error message. Running update-desktop-database doesn't change the situation; when run with the -v option, it doesn't show any unusual "foo lacks MimeType key" messages (i.e., for apps that should have a mimetype key).

Applications that are not part of Gnome, on the other hand, are still associated with the right filetypes - gvim with text files, OOo with documents, GIMP with images, etc.