FancyBox iframe returns parent.$ as undefined (using WordPress)
My answer is not related to wordpress, but one for fancybox in general.
in the iframe, if you have included the main jquery script(jquery-1.5.2.min.js), then it will conflict with the one on the main page, and parent.$.fancybox will not work in this case.
other jquery related stuff (like for eg: the tabs) will work inside the iframe.hence, it wont occur to a novice programmer that the second jquery script inside the iframe is the villain.