Computer blocked at CA Logon Shield

Document ID : KB000020621
Last Modified Date : 14/02/2018
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When a SD Job with option "Prevent user from being logged-on while job executes (WinNT only)" is sent to a computer, a logoff user is done and CA Logon Shield appears.
See screenshots below:
User could not logon until the SD job execution is teminated.

Figure 1

Figure 2

Sometimes if an error occurs during execution of SD Job, the CA logon Shield is never removed and user could not log on the computer anymore.

Rebooting the computer, cancelling the job in DSM does not change anything, the CA logon shield is still here and there is no way to logon.

The only possible logon is in safe mode.


IMPORTANT: This article contains information about modifying the registry.
Before you modify the registry, make sure to create a back up of the registry and ensure that you understand how to restore the registry if a problem may occur.
For more information about how to back up, restore, and edit the registry, please review the relevant Microsoft Knowledge Base articles on

  • Access the registry of the machine (remotely or directly on the machine by booting it in the safe mode).

  • Go under this registry Key:


    or on 64 bits machines:


  • Delete the following value:

    And update the value PreventLogon to 0:
    PreventLogon =0

  • This should unblock the machine and you should be able to logon again.