Sharepoint Daily Differentials not working in Backup Exec 2010

We run Symantec Backup Exec 2010 for our backups.  Most of the time this works fine and we have no issues.  However I've had a problem when Symantec Backup Exec trys to backup daily differential, it never works.  We get the following error..

2007SP Daily -- The job failed with the following error: The Backup Exec SQL Agent was not used to create the last full, differential, or log backup of this database. You must use the SQL Agent to run a full backup before you can run a differential backup or transaction log backup.

Now ok this would be an issue if the Weekly backup we run didn't work but they never fail, they are using the SQL Agent I need to know why the Differentials are not working and are always failing.  We have also tried to recreate the job for the Daily Differential but again no joy.

Any Ideas would be welcome...