i am awfully sorry for that
Ok, now, the code could be correct. It is not this your main problem. It is a problem of design. Always, the form's elments will overcover whichever other elements you might have in the page (for instance, a collapsed javascript menu, or even the background). z-Index will be of no help on this.
Same with Flash, if it's layout is not transparent. But if it is transparent, the problem will be backwards, you will be not be able to touch the form's element through the Flash's transparency . There might be some very intricate ways to solve those problems (but not always crossbrowser) so my advice is to modify the layout of the site, so that the expanded menu should not cover the form's elements.