[Plugin: comments] Comment error

I have this error message come up whenever anyone leaves a comment on my blog
Warning: call_user_func(gtcn_basic_callback) [function.call-user-func]: First argument is expected to be a valid callback in /hermes/web10/b65/moo.familyliciouscom/wp-includes/comment-template.php on line 1334

I was reading it is usually connected with Greg’s comment thread but I do not have that installed doeas anyone have any other ideas as to what it could be?

http://wordpress.org/extend/plugins/comments/