Error when cron job executes

I am running a tracker (CPVLab) the site works fine but there is a problem with a cron job. When the cron job executes I get an error:

2015/08/01 07:00:04 [error] 1303#0: *605 FastCGI sent in stderr: “PHP message: PHP Warning: unlink(/var/www/ Permission denied in /var/www/ on line 0” while reading response header from upstream, client:, server:, request: “GET /cron-wurfl.php HTTP/1.1”, upstream: “fastcgi://”, host: “

I set up the cron job using crontab -e as root, no other errors present but I did have issues with ionCube leaders to start with. Can anyone help please.