Never opens on first visit

Hi guys,

Colorbox never opens on first click, I get the loading screen and then a faded out screen with no image. If I close this and open it again it loads perfectly.
In order to see a gallery, I have to click on every picture once to get the faded out screen with no image and then reopen it to see the image. The slideshow feature only works once the image has been clicked on twice.

I was wondering if this might be a loading issue? Any ideas?

http://old.sussexsubaqua.co.uk/galleries

Thanks in advance