Ok, Lightbox is replaced with
Thickbox 2.0!
In my opinion, this is a far better option than Lightbox which is more bloaty.
The ThickBox.js + jQuery.js + CSS file only add an additional 28kb vs 105kb from Lightbox.
Thickbox 2.0 can display any inline content, iframed content, or content served through AJAX on the current page, not only images.
I have tested on x-cart 4.1.3 and product variants and Add to cart buttons works fine...and no javascripts errors.
Demo and download:
http://www.7dana.com/106.84.0.0.1.0.phtml