I just spent about an hour trying to debug this, but unfortunately I don’t have a specific answer for you. I downloaded a copy of your page, and I found that when I removed all the html from the body section of the document, except for the parts needed for shashin, everything worked fine and that error went away. You have a lot of javascript files being loaded on your site, and it’s not straightforward trying to track down all the interactions. There is something causing a conflict with Shashin. You could try turning off your other plugins and temporarily switching themes, and then incrementally turn everything back on, to see what triggers the conflict.
Also, this weekend I will uploaded a version of Shashin that fixes the original fancybox problem you reported. When that is ready you could switch back to using Fancybox, at least for now.