cron job failure email message

I run on Hostgator hosting company. I have installed Drupal 6.10, and have used their cpanel to run the cron jobs using the following command:

php -f '/home/USER/public_html/DOMAIN/cron.php'

(USER and DOMAIN are of course dummy names)

I receive an email each time, stating the following:

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent in /home/USER/public_html/DOMAIN/includes/bootstrap.inc on line 1029

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/USER/public_html/DOMAIN/includes/bootstrap.inc:1029) in /home/USER/public_html/DOMAIN/includes/bootstrap.inc on line 1029

This happens each time the cron job is run.

Please let me know if I am doing anything wrong, and what the solution is for this problem.

Thank you for your assistance.

Rick Stanley