Исправление проблемы apt-get - BADSIG

Иногда при apt-get update вылетает нехорошая ошибка типа:

W: GPG error: http://archive.ubuntu.com jaunty Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key [email protected]

W: A error occurred during the signature verification. The repository is not updated and the previous index files …