Unfortunately flash always takes precedence no matter what you do with z-index to my knowledge. I've seen some sites actually Hide their flash on mouseover and have a background which looks like a static version of the flash while the dropdown menus cover it. They used to use that on adobe.com.
The "fix" I posted is actually from the Adobe site - they have that solution there in their "help" files. I've given it quite often to people who use Son of Suckerfish dropdowns and have an issue with the dropdowns falling behind the flash object. Works just as well for other problems, too :) (And not just with Flash 9!)