wp-cron.php fails opening wp-load.php

My host suspended one of my websites for using up to much cpu resources.
The source of the problem was wp-cron.php being called on every page-load so I turned the internal cron off and opted for a hourly cronjob in directadmin instead.

Now the cronjob is executing wp-cron.php just fine, only it returns the following error:

Fatal error: require_once(): Failed opening required './wp-load.php' (include_path='.:/usr/local/lib/php') in /home/********/domains/cupcakesenmuffins.nl/public_html/wp-cron.php on line 26

Am I wrong to execute wp-cron.php directly through a cronjob?

Thanks for any advice you can give me,

Ron