On the panel I have two entries for the user interface menu. On the menu panel I see the same thing. Weirdly however nautilus shows me a Look and Feel menu with the same two entries (Applications, Dialogs) but also an MDI entry that is not visible elsewhere
Quite strange. MDI does appear in the control center, which is the same parser as the panel (but different parser from Nautilus). Fortunately it's just the MDI capplet, which should be removed anyway. ;-)
Caused by a missing file in control-center
Non-issue in gnome 2.