You may have already encountered this thread over on the NetWorker support forum, but it sounds exactly like what you've outlined here.  Please have a read through this one:  https://community.emc.com/message/437720

Dear Eric,

Thank you for your reply. But, unfortunatelly I cannot view the link you have sent me. The system says I am not allowed to view that page.

Could you please post any information you consider may help me, in this discussion?

Thank you

Do you have EMC Powerlink login capabilities?  That's what you would use to get to this linked discussion.  It ultimately is discussing a known issue/escalation. There are a couple of entries on this type of problem.  http://solutions.emc.com/emcsolutionview.asp?id=esg112248  and http://solutions.emc.com/emcsolutionview.asp?id=esg113111 (also will require Powerlink login).

These list this as a known issue.  One entry has a workaround, another says to "Contact EMC Technical Support for the NetWorker / NMDA module hotfix."

Here is the listed workaround.

Workaround

- Rename the lockbox directory in, for example, C:\Program Files\Legato\nsr\lockbox

- Delete the lockbox resource in Networker

- Create the a new instance of the client into a new test group

- Perform backup and confirm it works

- Delete old client instance and assign the new one to the correct group