Always on or allways visible problem

Hello guys,
i have a problem with my menu, i don't know yet if is a problem or i don't know how to change some settings but here is my problem :

in my site " zarnesti.net/galerie_foto.php " I have a lightbox photo gallery wich make the image (on click ) visible and the rest of site content invisible .
the problem is the menu is allways on top and visible , not invisible like rest of the site content
can you hel me ? the link is " zarnesti.net/galerie_foto.php " take a look .

tnx .

i found a problem like mine here : http://www.udm4.com/forum/showthread.php?t=643

so i've made some changes to z-order - from 1000 to 1 and now the menu is not over the images anymore !