Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.632
diff -u -r1.632 system.module
--- modules/system/system.module	14 Oct 2008 20:44:57 -0000	1.632
+++ modules/system/system.module	16 Oct 2008 09:28:28 -0000
@@ -940,7 +940,7 @@
     if (isset($files[$file->name]) && is_object($files[$file->name])) {
       $file->old_filename = $file->filename;
       foreach ($file as $key => $value) {
-        if (!isset($files[$file->name]) || !isset($files[$file->name]->$key)) {
+        if (!isset($files[$file->name]) || !isset($files[$file->name]->$key) || (defined('MAINTENANCE_MODE') && MAINTENANCE_MODE == 'update')) {
           $files[$file->name]->$key = $value;
         }
       }
Index: update.php
===================================================================
RCS file: /cvs/drupal/drupal/update.php,v
retrieving revision 1.263
diff -u -r1.263 update.php
--- update.php	12 Oct 2008 04:30:05 -0000	1.263
+++ update.php	16 Oct 2008 09:27:48 -0000
@@ -498,7 +498,7 @@
 
   // Store values of expensive functions for future use.
   if (empty($themes) || empty($modules)) {
-    $themes = _system_theme_data();
+    $themes = system_theme_data();
     $modules = module_rebuild_cache();
   }