weird firefox/safari problems with transparency and divs

I have "div1" holding a 1024x200px swf at the top of the page (left:
0px; top:0px; z-index: 3).

I have "div2" holding a 1024x568 swf 100px from the top of the page
(left: 0px; top:100px; z-index: 2).

div1 (a flash navigation bar at the top of the page with drop-down,
select menus) is suppose to overlap div2. Unfortunately, I cannot get
any button in div1 to rollover once the menus drops past the 100px
mark, which is where div2 starts. Its like div2 is preventing the div1
buttons from rolling over, even though div1 has a higher z-index. I
tried both regular flash buttons and movie clips. Does anyone have any
idea what's wrong? This problem shows up in Firefox and Safari but not
in Opera and Internet Explorer.

Any help appreciated.