Index: link-template.php
===================================================================
--- link-template.php	(revision 4996)
+++ link-template.php	(working copy)
@@ -387,7 +387,12 @@
 	if ( !$post )
 		return;
 
-	$title = apply_filters('the_title', $post->post_title, $post);
+	$title = $post->post_title;
+
+	if ( empty($post->post_title) )
+		$title = 'Previous Post';
+
+	$title = apply_filters('the_title', $title, $post);
 	$string = '<a href="'.get_permalink($post->ID).'">';
 	$link = str_replace('%title', $title, $link);
 	$link = $pre . $string . $link . '</a>';
@@ -403,7 +408,12 @@
 	if ( !$post )
 		return;
 
-	$title = apply_filters('the_title', $post->post_title, $post);
+	$title = $post->post_title;
+
+	if ( empty($post->post_title) )
+		$title = 'Next Post';
+
+	$title = apply_filters('the_title', $title, $post);
 	$string = '<a href="'.get_permalink($post->ID).'">';
 	$link = str_replace('%title', $title, $link);
 	$link = $string . $link . '</a>';