In the GLUT Atlantis demo, if you stop the animation
and move the mouse around with a menu open, the whales
jiggle but don't circulate. My guess is that you need
a way to redisplay the menu without forcing a window
redisplay from the application.
Menus do not display in single-buffered windows,
although they are active and the user can pick from
them if he knows how to move the mouse exactly right.