I need help with this error message that appears every 15 minutes. The error log shows no reference to it. Can anyone help with this? see message below.

From: root@box531.bluehost.com
Subject: Cron <fulldogg@box531> cd '/home/fulldogg/public_html/WebCalendar/tools/' ; /ramdisk/bin/php4 -q 'send_reminders.php' > /dev/null ;
Date: November 28, 2009 4:45:03 PM EST
To: fulldogg@box531.bluehost.com

/bin/sh: line 0: cd: /home/fulldogg/public_html/WebCalendar/tools/: