> z-index don't seem to work
Most likely that your image has a higher z-index than the dropdown. Can you check with Firebug/element inspector?
Solved it by using z-index -1;
Bit of a complicated layout as I had a <div> behind the <div> holding the rotating images set to width 100%. This had a background-color which was needed to stretch the width of the browser window.
When I set a z-index the <div> holding the rotating images went behind the <div> holding the background color BUT the drop menu worked.
Instead of using a solid background color for the <div> underlaying the rotating images I used a repeating background image with a transparent section in the middle where the images are positioned.
That did the trick, drop downs now appear!
Thanks for your input, most welcome. These little problems are sent to try our patience and resolve.