Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.358
diff -u -r1.358 form.inc
--- includes/form.inc	17 Aug 2009 19:14:39 -0000	1.358
+++ includes/form.inc	19 Aug 2009 03:33:20 -0000
@@ -2821,6 +2821,8 @@
 function batch_process($redirect = NULL, $url = NULL) {
   $batch =& batch_get();
 
+  drupal_theme_initialize();
+  
   if (isset($batch)) {
     // Add process information
     $url = isset($url) ? $url : 'batch';
@@ -2830,6 +2832,7 @@
       'url' => isset($url) ? $url : 'batch',
       'source_page' => $_GET['q'],
       'redirect' => $redirect,
+      'theme' => $GLOBALS['theme_key'],
     );
     $batch += $process_info;
 
Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.180
diff -u -r1.180 system.admin.inc
--- modules/system/system.admin.inc	17 Aug 2009 19:14:41 -0000	1.180
+++ modules/system/system.admin.inc	19 Aug 2009 03:33:33 -0000
@@ -1899,6 +1899,11 @@
 function system_batch_page() {
   require_once DRUPAL_ROOT . '/includes/batch.inc';
   $output = _batch_page();
+  
+  // Use the same theme that the page that started the batch.
+  $batch = &batch_get();
+  $GLOBALS['custom_theme'] = $batch['theme'];
+
   if ($output === FALSE) {
     drupal_access_denied();
   }