I have my wp debug mode turned on and I get a ton of php notices when loading a page after activating your plugin. All notices I have "noticed" have been coming from undefined indexes, I assume because of not checking "isset"..? Anyway, on line 351 and around line 80 in your main plugin file, I think you should fix this error which prevents the fancybox functionality from working properly.
As I turn the debug flag off, it all works perfectly. It is absolutely a great solution, but please consider fixing this so it works with the debug flag on.
My best / Joakim