--- modules/trigger/trigger.admin.inc.orig	2008-09-10 17:49:21.000000000 +0200
+++ modules/trigger/trigger.admin.inc	2008-09-10 17:46:38.000000000 +0200
@@ -81,8 +81,20 @@
 function trigger_unassign_submit($form, &$form_state) {
   $form_values = $form_state['values'];
   if ($form_values['confirm'] == 1) {
+    $hook = $form_values['hook'];
+    $op = $form_values['operation'];
     $aid = actions_function_lookup($form_values['aid']);
-    db_query("DELETE FROM {trigger_assignments} WHERE hook = '%s' AND op = '%s' AND aid = '%s'", $form_values['hook'], $form_values['operation'], $aid);
+    // actions module will not find actions that no longer exists
+    // even though they may still assigned
+    if (!$aid) {
+      $trgactions = _trigger_get_hook_actions($hook, $op);
+      foreach ($trgactions as $trgaid => $description) {
+        if (md5($trgaid) === $form_values['aid']) {
+          $aid = $trgaid;
+        }
+      }
+    }
+    db_query("DELETE FROM {trigger_assignments} WHERE hook = '%s' AND op = '%s' AND aid = '%s'", $hook, $op, $aid);
     $actions = actions_get_all_actions();
     watchdog('actions', 'Action %action has been unassigned.',  array('%action' => check_plain($actions[$aid]['description'])));
     drupal_set_message(t('Action %action has been unassigned.', array('%action' => $actions[$aid]['description'])));