Index: wp-includes/default-widgets.php
===================================================================
--- wp-includes/default-widgets.php	(revision 16913)
+++ wp-includes/default-widgets.php	(working copy)
@@ -650,6 +650,12 @@
  			$number = 1;
 
 		$comments = get_comments( array( 'number' => $number, 'status' => 'approve' ) );
+		$posts = array();
+		foreach ( (array) $comments as $comment) {
+			$posts[] = $comment->comment_post_ID;
+		}
+		$posts = array_unique($posts);
+		get_posts( array( 'post__in' => $posts, 'numberposts' => -1, 'update_post_meta_cache' => false, 'update_post_term_cache' => false, 'posts_per_page' => -1 ) );
 		$output .= $before_widget;
 		if ( $title )
 			$output .= $before_title . $title . $after_title;