German language pack does not translate buttons [solved]

The german language pack for German (DE_DE / "Deutsch") has a small error:
It does not translate any buttons. All the big blue buttons remain in english.

The solution is simple:
Rename the file /catalog/language/DE-DE/DE-de.php
to /catalog/language/DE-DE/default.php

Then it works. Each language packs seems to need a default.php. not a DE-de.php file in its root directory.