Exchange POP3 and ActiveSync stop working during Backup Exec 2012 backup process

Running Backup Exec 2012 with Backup Exec agent on Exchange Server 2003.

When the scheduled backup runs on the Exchange 2003 server, both POP3 access and ActiveSync (for smartphones) stops working. Regular email from Outlook works fine. When I cancel the backup, POP3 and ActiveSync almost immediately start working again. Anyone ever experienced this? Any solution? Suggestions?

Thanks