First of all your page loads much too slow. Try to use compression. You also use 15 external JavaScripts and 7 stylesheets and 20 external background images, thats quite a few HTTP Requests. You also mingle mootools with YUI. Why don't use just one Framework?
Enough nagging, now to your question: The milkbox is set up inside the iFrame, so in order to let the pics popup outside the iFrame you would have to alter Milkbox itself. That is 770 lines of JavaScript. Your best bet is to find the right method inside Milkbox, changing the target of the popUp to its parent frame; that is where the navigation and background picture resides in.
http://interplay2010.com/scripts/gallery/milkbox.js