First, update to the newest version of the theme if you're not already running it. Then try resetting the likes on the post that has negative count and if it happens again let me know.
Sorry for the late response, I'm not sure how to upgrade the site. I thought it would appear on wordpress. Could you provide a link to how to upgrade? I saw the instructions from upgrading themes from Made to Swag, but I didn't see how to upgrade theme. Please point me in the right direction because we still have negative likes.
See here: http://industrialthemes.ticksy.com/faq/1005