Backup Exec 2012 suddenly failing to backup Exchange DAG - no license - though we do have the license

Hi

We have a Backup Exec 2012 installation which has been happily backing up our Exchange 2010 DAG for the last few months. For some reason since last week the DAG backups have been failing stating 'The job failed with the following error: Before you can back up this source, you must purchase and install a license for the appropriate Backup Exec agent. See the Job Log for details'. We do have the Agent for Microsoft Exchange Server Licensed and Installed according to Backup Exec's license information report.

We have tried removing the licenses and re-adding them with no success.

Can anyone provide any advice/help?

Thanks

Adam