I had this same exact problem and jmfolcik’s solutions worked for me; from phpmyadmin I selected the database, then selected the wp_comments table and viewed it in “Structure” mode.
Oncer there I selected the “comments_date_gmt” field and checked the “index” option. Once I did that and it reported a success I checked my WordPress site and comments were back with no errors!
I did have to create an admin accoutn with higher privileges to make the change in the database, for some odd reason; but I didn’t have to change my site’s MYSQL login stuff in the wp-config file, which was good 🙂
Thanks a million jmfolcik!
