There is at least one GNOME theme (and it seems to me to be the default when you upgrade GNOME 2.2 to 2.4) that appears not to create a titlebar. Very annoying.
The solution, iirc, was to run 'metacity' in a terminal. This seemed to "reconnect" GNOME and Metacity for whatever reason. You might also try changing your window border settings in the (GNOME) Theme manager to use a different Metacity theme (maybe the one you are using is broken in some way), or in fact a different theme entirely (which would change not only the window borders, but the window controls, icons and desktop color theme as well).
Hope this helps.