I had the same Problem, solved it by upgrading to PHP 5, using a Parse-Request(?) in the .htaccess. – just two lines of code:
AddType x-mapp-php5 .php
AddHandler x-mapp-php5 .php
I’ve been putting them at the End of .htaccess, if you don’t have such a file you can easily create one with any kind of Texteditor. Then put it in the main WP-Directory using FTP.
Here’s where I found this Solution https://www.mbdealer.de/error-500-internal-server-error-bei-wordpress-2-8-x-und-11-als-webhoster – don’t know if it works allways, but it did in my case. It also fixed a returning Error 500 – Problem I’ve been encounting, now everything’s back to normal.
