Incompatible with the Custom Breadcrumb Module

URL admin/structure/custom_breadcrumbs/edit is not accessible.

Enhancing the function fast_404_validate_path_sql() in fast_404.inc with the following lines did the job for me:

if (count($path_parts) >= 4) {
  if ($path_parts[0] == 'admin' && $path_parts[1] == 'structure' && $path_parts[2] == 'custom_breadcrumbs' && $path_parts[3] == 'edit') {
        return TRUE;
  }
}