Using Mozilla 1.3, same for me…
Mouseover the menu and it opens. Then go all the way down, and exit the pulldown menu on the bottom and it dissapears.
Now do the same but exit the pulldown menu by going out of it left or right and the menu stays on the screen.
Already confirmed this earlier.
Menu’s stay on screen when you move left right or above. Move down past the menu’s however and they will vanish.