auto-close comments errors

Since I’ve istalled auto-close comments, everytime somebody tries to leave a comment, they get the following message after pressing ‘Say It!’:
Warning: Unknown modifier ‘C’ in /usr/local/psa/home/vhosts/kinuk.co.uk/httpdocs/blog/wp-includes/functions.php on line 1348
[Moderated – repeat errors removed]
I’ve tried looking for solutions…and it said to delete any white space in the autoclose.php file. Tried that…didn’t work. I’ve now deleted autoclose.php and the message still appears whenever a comment is posted.
The comments do get through, but how do I get rid of this page that pops up? Was it the auto-close that did this or did I make a mistake somewhere along the way?
Thanks for any help on trying to explain the meaning of this…it’s become rather frustrating.