Not yet since z-index only works for absolute positioning, my page layout is using relative positioning….
z-index is a value of all three: absolute, fixed and relative positioning, but, this problem might be more related to your Flash content’s window mode. Unfortunately, it’s been my experience that drop-down menus that go over top of Flash content are difficult to deal with.
If you have control over this Flash content and you can change its properties, try changing the “wmode” to “transparent”, and if that doesn’t work, try changing it to “opaque”. If you don’t have control over the Flash content (for example if this is some kind of 3rd party Flash advertisement/banner), you might want to look into writing some JavaScript that will hide the Flash content when a drop-down goes over top of it.
About two-and-a-half years ago, I went through A LOT of testing with the original Suckerfish drop-downs and Flash content. I worked for a newspaper at the time and we were implementing a horizontal navigation that had drop-downs and had a leaderboard (728x90) banner ad directly below the nav. Everything worked great until we encountered 3rd party Flash banners and, in IE6, select boxes in forms.
After all of that crazy testing, we purchased the Milonic menu, and the network of sites at the newspaper still use it. I won’t give out the URL for the place where I worked, but I know that the Minneapolis Star Tribune used Milonic (and still might), and they had to write some JavaScript to hide their Flash banners when the drop-downs intersected them.
Sorry this is long-winded, but I hope it helps you a bit. It’s been a while since I’ve dealt with drop-downs (thank GOD!), but I definitely sympathize with your situation.
Let us know if you get it sorted.