Header-object/logo to show in front of Slideshow

I have created my template using artisteer and put the company logo on using the tag header-object. The slideshow appears fine and in the right place but appears over the logo. Do you know a way to make sure my logo stays at the front before the slider. I have tried altering the style sheet to include a z-index but this hasn’t changed anything.

http://wordpress.org/extend/plugins/header-slideshow/