This works also great in Netscape 4.78 (the one I tested).
Having divs over Flash movies does not work in IE either. The solution that they have here is that when they show a menu they hide the flash and show an image instead. This does not happen in Mozilla cause of their code i guess. So this should ve INVALID or dupe of bug 93959?
Then this is a dupe of bug 110441. And the reason for that is in http://bugzilla.mozilla.org/show_bug.cgi?id=110441#c32
Actually, this is a dup of an evang bug... *** This bug has been marked as a duplicate of 117370 ***