Index: wp-includes/update.php
===================================================================
--- wp-includes/update.php	(revision 8941)
+++ wp-includes/update.php	(working copy)
@@ -273,11 +273,11 @@
 add_action( 'admin_init', '_maybe_update_themes' );
 add_action( 'wp_update_themes', 'wp_update_themes' );
 
-if ( !wp_next_scheduled('wp_update_plugins') )
+if ( !wp_next_scheduled('wp_update_plugins') && !defined('WP_INSTALLING') )
 	wp_schedule_event(time(), 'twicedaily', 'wp_update_plugins');
 
 
-if ( !wp_next_scheduled('wp_update_themes') )
+if ( !wp_next_scheduled('wp_update_themes') && !defined('WP_INSTALLING') )
 	wp_schedule_event(time(), 'twicedaily', 'wp_update_themes');
 
 ?>