--- wp-includes/comment.php~	2009-12-21 11:46:30.000000000 -0600
+++ wp-includes/comment.php	2010-12-23 09:35:38.596027997 -0600
@@ -1590,5 +1590,5 @@
 				$pinged[] = $tb_ping;
 			} else {
-				$wpdb->query( $wpdb->prepare("UPDATE $wpdb->posts SET to_ping = TRIM(REPLACE(to_ping, '$tb_ping', '')) WHERE ID = %d", $post_id) );
+				$wpdb->query( $wpdb->prepare("UPDATE $wpdb->posts SET to_ping = TRIM(REPLACE(to_ping, %s, '')) WHERE ID = %d", $tb_ping, $post_id) );
 			}
 		}