In this sample:
When you are using IE6 or IE7 and maxime a window, the menu appears behind.
Also when I use IE or IE7 I have a restrictionzone but when I create a new window, it doesnt respect the restrictionzode and the menu always appears behind the window.
I have z-index in the correct order, but this behavior is still present.
With IE8 all works fine. The problem is I have customers with Ie6 and IE7.