symantec backup - e00002f7 - Cannot extract mailbox messages from the Exchange backup.

we have 2 exchange servers in a dag in 2 separate datacenters across 2 separate subnets.  both centers are connected via 100 mb fibre circuit.   symantec bkup exec is installed on the server in Houston and the remote bkup agent on the server in New York.  When all databases are mounted on the Houston server, all the backups succeeed.    However, when we mount the databases for the new york users in New York, and run the backups for the new york databases i get the error message:

e00002f7 - Cannot extract mailbox messages from the Exchange backup.  Review the job log for more information.For additional information regarding this error refer to link V-79-57344-759

I've googled this error and the resolution on symantec website suggests excempting the c:\temp\backup exce drive.  However,  the situation doesn't apply to us.  we don't have an AV scanning that folder.  

Does anyone have any further suggestions?