I\'ve just determined using Firebug that when Fancybox window is created it actually takes all of my ASP.NET controls (contained in DIV tag) and puts them outside FORM tag.
Fancybox Version: 2.1.2
Line 1782 of jquery.fancybox.js
Change this:
this.el = document.all && !document.querySelector ? $('html') : $('body');
To this:
this.el = document.all && !document.querySelector ? $('html') : $('form:first');