The javascript is getting an error when it tried to read the size of the images. One of the large images has a url of a2_670p.jpg which is not found. That url looks correct, so my guess is you need to recreate the images for your gallery.
You can do that by logging in to the admin, select your gallery, go to the settings, and click update watermark. That will create your new 670p size and should fix the issue.