Exchange 2010 Transaction logs not Truncated after full backup

I have 2010 Exchange server with 1 database and no DAG.  I am using Symantec Backup Exec 2010.  My Exchange backup settings are for a full backup (truncate logs).  For some reason the logs are not being truncated (deleted).  I believe this is a relatively simple configuration of my exchange server and the logs should be deleted once my daily backup completes.  Can someone tell me where to look for the problem?  Most questions include DAG configurations.

Thanks,

WWWIII