I had the same problem with our blog at https://blog.stegplatten.info hosted at 1and1.
I think it has something todo with their switching to PHP 5.2+
I solved the problem by changing an entry i the .htaccess file from
AddType x-mapp-php5 .php
AddHandler x-mapp-php5 .php
to
AddType x-mapp-php6 .php
AddHandler x-mapp-php6 .php
Regards,
Michael from https://www.rexin-shop.de
