Sorry for posting in a resolved thread.
I have the same issue, the lightbox doesn't kick in. I'm quite sure there are some dependencies missing because the lightbox feature works with no problems if NextGEN plugin is enabled. If I disable nextgen the chrome debugger says Uncaught TypeError: Cannot read property 'msie' of undefined from the fancybox pack js file referring to lines 18 and 46 of that file as anonymous function.
There is also another error from the image-tiles.js file: Uncaught TypeError: undefined is not a function. This error refers to lines 13 and 2 of the file as anonymous function and to jquery min file. In jquery it refers to n.extend.each, n.fn.n.each, j, k.fireWith, n.extend.ready and finally to K.
If you'd need any more info please let me know. Thanks in advance for your help!