NTBackup of Exchange 2003

I have an Exchange 2003 server on a Windows 2003 server I tried to do a backup of Exchange not a restore and I keep getting this error.
Source: ESE BACKUP
Catagory: Callback
Event ID: 904

Information Store (2312) Callback function call ErrESECBPrepareInstanceForBackup ended with error 0xC7FE1F45 Instance not found.

I keep finding stuff or a restore but not on just doing a backup. Sure could use some help on this.