diff -rau a/modules/file/file.module b/modules/file/file.module
--- a/modules/file/file.module	2010-11-13 11:04:08.000000000 -0300
+++ b/modules/file/file.module	2010-11-27 16:36:00.633388800 -0300
@@ -528,7 +528,10 @@
   // If referencing an existing file, only allow if there are existing
   // references. This prevents unmanaged files from being deleted if this
   // item were to be deleted.
-  $clicked_button = end($form_state['clicked_button']['#parents']);
+  $clicked_button = '';
+  if (!empty($form_state['clicked_button'])) {
+    $clicked_button = end($form_state['clicked_button']['#parents']);
+  }
   if ($clicked_button != 'remove_button' && !empty($element['fid']['#value'])) {
     if ($file = file_load($element['fid']['#value'])) {
       if ($file->status == FILE_STATUS_PERMANENT) {