Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.841
diff -u -p -r1.841 common.inc
--- includes/common.inc	30 Dec 2008 16:43:14 -0000	1.841
+++ includes/common.inc	2 Jan 2009 21:04:09 -0000
@@ -3188,9 +3188,10 @@ function drupal_alter($type, &$data) {
  *   The rendered HTML.
  */
 function drupal_render(&$elements) {
-  if (!isset($elements) || (isset($elements['#access']) && !$elements['#access'])) {
+  if (!isset($elements) || (isset($elements['#access']) && !$elements['#access']) || isset($elements['#rendered'])) {
     return NULL;
   }
+  $elements['#rendered'] = TRUE;
 
   // If the default values for this element haven't been loaded yet, populate
   // them.