Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.486
diff -u -p -r1.486 form.inc
--- includes/form.inc	30 Aug 2010 05:52:35 -0000	1.486
+++ includes/form.inc	30 Aug 2010 17:35:55 -0000
@@ -2791,6 +2813,11 @@ function theme_tableselect($variables) {
       drupal_add_js('misc/tableselect.js');
       array_unshift($header, array('class' => array('select-all')));
     }
+    else {
+      // Add an empty header when radio buttons are displayed or a "Select all"
+      // checkbox is not desired.
+      array_unshift($header, '');
+    }
   }
   return theme('table', array('header' => $header, 'rows' => $rows, 'empty' => $element['#empty'], 'attributes' => $element['#attributes']));
 }