Flash Element and CSS Menu

Ok, so I have a few site utilizing various sorts of javascript drop-down menus. A few of those have flash elements, swf files, movies, etc. underneath them. Very often the menu will disappear behind the movie elements in a flickering fashion or just fully disappear.

This isn’t a wmode=transparent sort of issue (nor is the movie improperly embedded).
This isn’t a z-index issue - I’ve tried all sorts of variations to no avail.
It doesn’t happen on all browsers. I notice most often on PowerPC macs using FireFox, but I have also seen other browsers and operating systems do this randomly.

I can’t track down the issue. I’m hoping someone might read this and recognize what I am talking about. Any help would be great. I’m dying to fix this and I can’t figure it out.