I think it might be the transparent thing that firebug sees:
HTML Code:
div#menu1 { background: url("http:/greindustries.co.za/wp-content/themes/atahualpa/images/pagemenu-background.png") repeat scroll 0 0 transparent !important;
HTML Code:
div#menu1 { background: url('http:/greindustries.co.za/wp-content/themes/atahualpa/images/pagemenu-background.png') !important }
I can unfortunately not give the url to the site as I have a under construction 503 - Service Unavailable set up for the page.
Thanks in advance!