Comment 9 for bug 560082

After changing the Desktop Effects, or logging in without title bars, could you check the setting of /desktop/gnome/session/required_components/windowmanager with gconf-editor and verify that it shows the same as Desktop Effects:
* It should say metacity if Desktop Effects are set to None
* Otherwise it should say compiz

Also, you could try changing Desktop Effects while running gnome-appearance-properties in a terminal and see if it outputs some useful information.