Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 11902)
+++ wp-includes/post.php	(working copy)
@@ -1798,6 +1798,8 @@
 /**
  * Given the desired slug and some post details computes a unique slug for the post.
  *
+ * @global wpdb $wpdb
+ * @global WP_Rewrite $wp_rewrite
  * @param string $slug the desired slug (post_name)
  * @param integer $post_ID
  * @param string $post_status no uniqueness checks are made if the post is still draft or pending
@@ -1808,7 +1810,10 @@
 function wp_unique_post_slug($slug, $post_ID, $post_status, $post_type, $post_parent) {
 	if ( in_array( $post_status, array( 'draft', 'pending' ) ) )
 		return $slug;
-	
+	/*
+	 * @var $wp_rewrite WP_Rewrite 
+	 * @var $wpdb wpdb 
+	 */
 	global $wpdb, $wp_rewrite;
 	$hierarchical_post_types = apply_filters('hierarchical_post_types', array('page'));
 	if ( 'attachment' == $post_type ) {
@@ -1831,7 +1836,11 @@
 		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type IN ( '" . implode("', '", $wpdb->escape($hierarchical_post_types)) . "' ) AND ID != %d AND post_parent = %d LIMIT 1";
 		$post_name_check = $wpdb->get_var($wpdb->prepare($check_sql, $slug, $post_ID, $post_parent));
 		
-		if ( $post_name_check || in_array($slug, $wp_rewrite->feeds) ) {
+		$feeds = $wp_rewrite->feeds;
+		if ( is_null($feeds) )
+			$feeds = array();
+	
+		if ( $post_name_check || in_array($slug, $feeds) ) {
 			$suffix = 2;
 			do {
 				$alt_post_name = substr($slug, 0, 200-(strlen($suffix)+1)). "-$suffix";
@@ -1845,7 +1854,11 @@
 		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = %s AND ID != %d LIMIT 1";
 		$post_name_check = $wpdb->get_var($wpdb->prepare($check_sql, $slug, $post_type, $post_ID));
 		
-		if ( $post_name_check || in_array($slug, $wp_rewrite->feeds) ) {
+		$feeds = $wp_rewrite->feeds;
+		if ( is_null($feeds) )
+			$feeds = array();
+
+		if ( $post_name_check || in_array($slug, $feeds) ) {
 			$suffix = 2;
 			do {
 				$alt_post_name = substr($slug, 0, 200-(strlen($suffix)+1)). "-$suffix";