Earlier I was working on a Zen Cart site and ran into an issue installing the Ultimate SEO URL add-on. The Ultimate SEO URL add-on creates more SEO(Search Engine Optimization) friendly URL’s for Zen Cart. The site in question already had a previous version of the Ultimate SEO URL add-on installed and once I was finished the front-end of the site was working perfectly with the new SEO friendly URL’s. The problem was when I attempted to login to the admin portion of the Zen Cart site I was receiving a “500 – Internal Server Error” message. Below I have noted information on what was done to troubleshoot the problem as well as how the problem was resolved.