Double lightbox, remove one

Hi!
I am using fancybox to add a lightbox to single images.
I am also using galleries with integrated lightbox function, now when u click on one gallery thumbnail it opens two lightboxes…. How can I disable one of them?
Please see this post for example The single image at top pops up one lightbox, the gallery images pop up two lightboxes….

Would be great if someone can help me with this.

Thanks!