Index: wp-includes/category.php
===================================================================
--- wp-includes/category.php	(revision 4721)
+++ wp-includes/category.php	(working copy)
@@ -5,7 +5,7 @@
 
 	if ( ! $cat_ids = wp_cache_get('all_category_ids', 'category') ) {
 		$cat_ids = $wpdb->get_col("SELECT cat_ID FROM $wpdb->categories");
-		wp_cache_add('all_category_ids', $cat_ids, 'category');
+		wp_cache_set('all_category_ids', $cat_ids, 'category');
 	}
 
 	return $cat_ids;
@@ -148,7 +148,7 @@
 	} else {
 		if ( ! $_category = wp_cache_get($category, 'category') ) {
 			$_category = $wpdb->get_row("SELECT * FROM $wpdb->categories WHERE cat_ID = '$category' LIMIT 1");
-			wp_cache_add($category, $_category, 'category');
+			wp_cache_set($category, $_category, 'category');
 		}
 	}
 
Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 4721)
+++ wp-includes/post.php	(working copy)
@@ -902,7 +902,7 @@
 
 	if ( ! $page_ids = wp_cache_get('all_page_ids', 'pages') ) {
 		$page_ids = $wpdb->get_col("SELECT ID FROM $wpdb->posts WHERE post_type = 'page'");
-		wp_cache_add('all_page_ids', $page_ids, 'pages');
+		wp_cache_set('all_page_ids', $page_ids, 'pages');
 	}
 
 	return $page_ids;
@@ -944,7 +944,7 @@
 					return get_post($_page, $output);
 				// Potential issue: we're not checking to see if the post_type = 'page'
 				// So all non-'post' posts will get cached as pages.
-				wp_cache_add($_page->ID, $_page, 'pages');
+				wp_cache_set($_page->ID, $_page, 'pages');
 			}
 		}
 	}