I found the latest version of jQuery UI(1.10) remove the zIndex option. And it\'s confirmed on the jQuery website.
zIndex
It really shocked me. Please think ab
Have you tried using the "appendTo" option? Just dynamically add a wrapper with a z-index of what you need it to be, then use the id of that element as the selector in the "appendTo" argument.
http://api.jqueryui.com/dialog/#option-appendTo