I thought it was worth mentioning that on the cron examples you see in the documention and other places on the net such as this example.

wget -q -O /dev/null http://www.yoursite.com/ow_cron/run.php

that there may not be an -O (or -o) option on your server.   When i ran the -O it came back and said that there was no such option so i just went with the standard

php -q  /home/username/public_html/ow_cron/run.php

also a reminder that you want to remove the -q when you first set this up so that you will get the email (assuming you have put an email in the notify block of the cron setup page).  One you get the email open it and make sure everything looks ok and no errors.  Then put the -q back... -q is for quiet mode so that you dont get an email each time it runs.

hope this helps :)