Your theme has the FancyBox extension script already included. It is not compatible with my plugin since only one instance of the jQuery extension is allowed.
You need to either hack your theme to remove the fancybox inclusion or disable Easy FancyBox and convert your youtube link so that it uses the is theme included one.
<a href="http://www.youtube.com/v/xi3ONCJT-II" target="_blank" class="fancybox iframe"><img src="http://ashdance.com/wp-content/uploads/2012/09/ash-vid.jpg" style="border:2px solid #e4e4e4; margin:10px 0 20px;" /></a>
should make it work with the theme included version...