Exchange 2003

I am using Windows server 2003 with Exchange 2003. I am the Administrator for our comapany. I am using the Symanctec Backup 11d edition. When I back up the exchange only my mailbox is not getting backed up. Everybody’s mailbox is backedup. When I go to exchange manager my mailbox is in the storage place. The same storage I backedup many times..but of no use. Could anyone help me pls.