[Plugin: NextGEN Gallery] Z-index on NextGen-Gallery

I am using NextGen-Gallery with a WP theme called Luxury which is based on the 960gs… When I view the overlay effect from a photo gallery, it actually appears below (behind) the thumbnails and the content. I think this is to do with z-index of the overlay layer. Is there someplace in the css of NextGen I can set the z-index to a very high level so this is not longer an issue. I have looked and can’t find z-index anywhere.

Thanks