I seem to be having a similar problem with my site here is a link:
jeremygarrett.com/index.php/artwork/personal-work/personal-work/personal-work-1-19
The gallery use to work properly, although it has been over a year since I've worked on this site, and I noticed that the larger detailed views were not displaying as the once did. Today I updated joomgallery.
The thumbnails in the motiongallery carousel shows properly; however, some of them such as the first one does not show the detailed view of the image and get hung up trying to load it.
As a test I re-uploaded the last image in the carousel entitled "Smile_1". The numbnail in the carousel is displaying properly, but the larger original image and the slimbox detail views are broken and not displaying.
I read through the link you provided and disabled all plugins to no avail. I appreciate any help you can provide.