"If using an absolute URL, make sure it starts with 'http://' (e.g. http://www.example.com rather than just www.example.com)."
Tried it both ways and neither works.
"Also, make sure that there are no elements on your web page which are obscuring/overlapping your gallery's Back Button rendering it non-functional."
It's a very simple site with only two pages and the gallery, so I don't think there's anything obscuring/overlapping the SV back button but I'm open to suggestions as to what to look for and where.
"If you continue to experience difficulties, please post the URL to your gallery so that I can take a look."
click on photography gallery
As you'll see, the "exit gallery" link goes to my host's error page. At that point, the local path to the index file has somehow been added to the end of the URL. I'm not putting the local path in the SV "back button URL" box, just the absolute URL. The local path seems to be getting automatically added but I can't figure out how to stop it from doing this.