=== modified file /modules/comment/comment.admin.inc ===
index 14d17fa..6906e0d 100644
--- /modules/comment/comment.admin.inc
+++ /modules/comment/comment.admin.inc
@@ -130,6 +130,7 @@ function comment_admin_overview($form, &$form_state, $arg) {
     '#header' => $header,
     '#options' => $options,
     '#empty' => t('No comments available.'),
+    '#default_value' => array(),
   );
 
   $form['pager'] = array('#theme' => 'pager');