I'm having a z-index order issue.

I thought it would be an easy fix and I have tried a few different z-index changes, but I cant seem to get it right.
The issue is just the home page:

http://www.jamesgradwell.com/staging.
as the jquery dropdown menu is falling behind the other jquery image slider.
(what is also odd is that at times, it comes in the front and then it goes behind again)

Could anyone please assist me? it would be much appreciated!
thanks
Leigh