Error message when submitting review

I have been unsuccessful in submitting any reviews since joining. All attempts are met with this error message:

Fatal error: Call to a member function unlock_tables() on a non-object in /home/bdsmlibr/public_html/forums/includes/functions.php on line 4936

This error message appears instead of a "submit" button at the bottom of review screen. It appears regardless if I use Internet Explorer or Firefox browser. My browsers are set to allow session cookies. Has anyone seen this problem or know what browser settings might fix?