Index: wp-includes/comment.php
===================================================================
--- wp-includes/comment.php	(revision 6637)
+++ wp-includes/comment.php	(working copy)
@@ -992,7 +992,7 @@
 	}
 
 	// Do Trackbacks
-	$trackbacks = $wpdb->get_results("SELECT ID FROM $wpdb->posts WHERE to_ping <> '' AND post_status = 'publish'");
+	$trackbacks = $wpdb->get_col("SELECT ID FROM $wpdb->posts WHERE to_ping <> '' AND post_status = 'publish'");
 	if ( is_array($trackbacks) ) {
 		foreach ( $trackbacks as $trackback )
 			do_trackbacks($trackback->ID);