[Koha] Overdue notifications not being sent out

Hi folks, I need someone to point the way here. We are running koha 3.02 on Ubuntu 10.04 LTS. The server is configured to send email using sendmail via a smarthost. I have run a series of tests and established that the system has no issues in forwarding email. However in koha, the system is sending out notifications for new accounts and reservations, but not overdue notifications and reminders. When i check some of the patron's notices, i find too many pending notifications. We have configured messaging appropriately, added the email notifications to cron and it used to work well until we upgraded from koha 3.0. So what could we have done wrong? what can i do to fix this and purge all pending notifications? Regards, Benson