Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 3494)
+++ wp-includes/functions.php	(working copy)
@@ -2283,4 +2283,8 @@
 	return $wpdb->num_queries;
 }
 
+function deactivate_plugins() {
+	update_option('active_plugins', array());
+}
+
 ?>
Index: wp-settings.php
===================================================================
--- wp-settings.php	(revision 3494)
+++ wp-settings.php	(working copy)
@@ -170,7 +170,7 @@
 		require(ABSPATH . '/my-hacks.php');
 }
 
-if ( get_settings('active_plugins') ) {
+if ( get_settings('active_plugins') && !defined('WP_INSTALLING') ) {
 	$current_plugins = get_settings('active_plugins');
 	if ( is_array($current_plugins) ) {
 		foreach ($current_plugins as $plugin) {
Index: wp-admin/upgrade.php
===================================================================
--- wp-admin/upgrade.php	(revision 3494)
+++ wp-admin/upgrade.php	(working copy)
@@ -75,6 +75,7 @@
 	break;
 	
 	case 1:
+	deactivate_plugins();
 	wp_cache_flush();
 	make_db_current_silent();
 	upgrade_all();