The comments worked with the plugins disabled. I wonder why this would start happening all of a sudden?
I have the same problem and it just started happening. I looked and found that it is dying on the call to wp_new_comment() in wp-comments-post.php. But, I can’t find where this function is defined. I am using 1.5.2 and the URL is http://www.roythepug.com if anyone wants to see.
