Comment SQL error

I hope someone knows the answer to this. I tried searching but haven’t found a duplicate yet.

Whenever someone tries to leave a comment at my site, they get a long series of errors:


WordPress database error: [You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE comment_ID = 506' at line 1]
UPDATE wp_comments SET comment_reply_ID= WHERE comment_ID = 506;

Warning: Cannot modify header information - headers already sent by (output started at /home/martytdx/public_html/zealot/wp-includes/wp-db.php:98) in /home/martytdx/public_html/zealot/wp-comments-post.php on line 51

Warning: Cannot modify header information - headers already sent by (output started at /home/martytdx/public_html/zealot/wp-includes/wp-db.php:98) in /home/martytdx/public_html/zealot/wp-comments-post.php on line 52

Warning: Cannot modify header information - headers already sent by (output started at /home/martytdx/public_html/zealot/wp-includes/wp-db.php:98) in /home/martytdx/public_html/zealot/wp-comments-post.php on line 53 ...

...
Warning: Cannot modify header information - headers already sent by (output started at /home/martytdx/public_html/zealot/wp-includes/wp-db.php:98) in /home/martytdx/public_html/zealot/wp-comments-post.php on line 58

Warning: Cannot modify header information - headers already sent by (output started at /home/martytdx/public_html/zealot/wp-includes/wp-db.php:98) in /home/martytdx/public_html/zealot/wp-includes/pluggable-functions.php on line 129

Anyone seen something similar and know how to fix it? I tried the Zend Optimizer fix someone suggested, but the errors are still there. The Blog is at https://www.martytdx.com/zealot.
Any help would be greatly appreciated!

Marty