=== modified file modules/comment/comment.admin.inc ===
--- modules/comment/comment.admin.inc	2010-09-16 15:28:30.000000000 +0530
+++ modules/comment/comment.admin.inc	2010-09-16 15:23:09.000000000 +0530
@@ -141,7 +141,7 @@ function comment_admin_overview($form, &
  * Validate comment_admin_overview form submissions.
  */
 function comment_admin_overview_validate($form, &$form_state) {
-  $form_state['values']['comments'] = array_diff($form_state['values']['comments'], array(0));
+  $form_state['values']['comments'] = is_array($form_state['values']['comments']) ? array_diff($form_state['values']['comments'], array(0)) : array();
   // We can't execute any 'Update options' if no comments were selected.
   if (count($form_state['values']['comments']) == 0) {
     form_set_error('', t('Select one or more comments to perform the update on.'));