Because in:
Config::Set('FSFK_FTP_SERVER', 'ftp://server72.hosting2go.nl/subdomains/va/httpdocs/lib/fsfk');
You have to put the path to the lib/fsfk folder after the ftp server. So if you FTP to your server, and you start in the home folder, then inside that you have public_html, and inside that it's phpvms and then lib/fsfk you put
ftp://my.ftp.server.com/public_html/phpvms/lib/fsfk