you can do the following steps to resolve the issue.
update to the latest MDAC version 2.8.
for the same , go to the following link:
http://www.microsoft.com/downloads/details.aspx?FamilyID=6c050fe3-c795-4b7d-b037-185d0506396c&DisplayLang=en
then you can update to the latest jet pack ver 4 service pack 8 for the same , go to the following link:
http://www.microsoft.com/downloads/details.aspx?familyid=1e268b39-533e-48b0-b8d7-1781befde1f8&displaylang=en
Please install Backup Exec 9.1 Service pack 1 after upgrading to 9.1 from the following link:
http://seer.support.veritas.com/docs/267182.htm
Before starting the backup services, please disable the anti vrus for isolation purposes and verify the results.
We hope this helps.