and seven different stylesheets (not counting the print.css), seriously how do you expect anyone (even yourself!) to be able to identify which rule needs to be changed? That’s the biggest problem with using a cheap CMS and all sorts of ‘clever’ widgets – they fill the code with so much carp* that it’s nigh-on impossible to figure out what’s what. You seem to have z-index in the right place and appropriate elements positioned, so I’m afraid I’m stuck…
(No doubt I will no be proven wrong by someone cleverer than I who can see exactly what’s causing the problem)