I just upgraded ZenPhoto to the latest 1.6.5 and decided to work on a new theme. I am trying to get zpBootstrap v2.3 running, but am having an issue. I activate it and go in a check the settings, and all looks normal. The problem is when I visit the site with it active, I get a HTTP Error 500. Am I missing an addon I need for this theme or something?

The original theme is not maintained anymore. Try using our roughly fixed fork which internally is kind of 2.3.2? https://github.com/zenphoto/zpBootstrap