Categories disappeared causing posts to disappear

http://www.parkwaydrivemerch.com

Has anyone experienced losing their categories in the wp-admin causing their posts to not appear on their site?

Between my site functioning and not functioning, the only change I’ve made is to activate and deactivate the Google XML Sitemap plugin. Everything else seems to work fine including all other plugins.

I think it could have something to do with writing to the database???