I have the same issue (in Drupal) of the Superfish menu appearing across the middle of the gallery when expanding to fullscreen mode. It worked up until at least a couple of versions ago. I tried the suggestions above.
Setting transparency did not fix the issue (it might if I change the z-index also, but that might affect things elsewhere on my site).
The expandInNewPage="TRUE" option worked for IE and Chrome, but in Firefox, there was no way to close the gallery. Using the CLOSE button just caused the gallery to relaunch in fullscreen mode, and the browsers back button did the same. The only way I could fix it was to remove the fullscreen option. That's OK, because it still goes fullscreen on the Iphone, but I can no longer go fullscreen in a browser.
Something changed, because this used to work. I will also post over in the Drupal module support forum.
......................................
UPDATE:
I think I got it.
User xopherus suggested this CSS in the Drupal forum:
/* Horizontal Menu */
#menu-bar {
position: relative;
z-index: 2;
}
/* Content Area */
.region {
position: relative;
z-index: 1;
}
-- I tried that, but it kept my menus from displaying at all, so I removed the z-index properties from each item, and in Juicebox config., set:
expandInNewPage="TRUE"
showExpandButton="TRUE"
Everything seems fine now. Sorry for the long message. Hope it's ok to cross-post like this, and it helps someone else who might be having the same issues. Thanks for the support forum, and thanks to Drupal user xopherus for posting his solution too.