I am having the same issue as well. My error code is:
Fatal error: Uncaught Exception: 190: Invalid OAuth access token signature. thrown in /home/content/51/5453851/html/blog/wp-content/plugins/seo-facebook-comments/facebook/base_facebook.php on line 1273
I am using the prophoto4 WP theme that sometimes interferes with plug ins. Could this be related?