Index: wp-includes/comment.php
===================================================================
--- wp-includes/comment.php     (revision 6405)
+++ wp-includes/comment.php     (working copy)
@@ -334,7 +334,7 @@
        extract($commentdata, EXTR_SKIP);

        if ( ! isset($comment_author_IP) )
-               $comment_author_IP = preg_replace( '/[^0-9., ]/', '',$_SERVER['REMOTE_ADDR'] );
+               $comment_author_IP = preg_replace( '/[^0-9a-fA-F:., ]/', '',$_SERVER['REMOTE_ADDR'] );
        if ( ! isset($comment_date) )
                $comment_date = current_time('mysql');
        if ( ! isset($comment_date_gmt) )
@@ -389,7 +389,7 @@
        $commentdata['comment_post_ID'] = (int) $commentdata['comment_post_ID'];
        $commentdata['user_ID']         = (int) $commentdata['user_ID'];

-       $commentdata['comment_author_IP'] = preg_replace( '/[^0-9., ]/', '',$_SERVER['REMOTE_ADDR'] );
+       $commentdata['comment_author_IP'] = preg_replace( '/[^0-9a-fA-F:., ]/', '',$_SERVER['REMOTE_ADDR'] );
        $commentdata['comment_agent']     = $_SERVER['HTTP_USER_AGENT'];

        $commentdata['comment_date']     = current_time('mysql');