I'm using the latest version of Nice Menus with Drupal 5.2, and IE 6/7 consistently displays the fly-out sub menus behind an absolutely positioned content div just under the menu bar (see attached image). I initially thought this was a wmode issue since the content is a Flash slideshow, but I have since swapped it out with a static image and the issue persists. I have also tried relative position on the div, to no effect, and I have changed the z-index of the both the div and the menu block.
I am using a third party theme, and the menu works perfectly in FF, Opera, Safari, and Konqueror.
Any advice would be greatly appreciated.