maybe that's no solution but does the error still occur if you switch the board language to german?
If so, there might be an error in the file language/en/acp/common.php.
The file has to start with
Code: Alles auswählen
<?php
The uploadmode of your ftpclient could be another reason for this error. Try changing ascii to binarymode.
Hope it works.

Kind regards,
Schorsch