Because of a security error, the client could not connect to the Terminal server

This article provides a solution to an issue where Terminal Services clients are repeatedly denied access to the terminal server after upgrade Windows.

Applies to:   Windows Server 2012 R2
Original KB number:   329896


After you upgrade a Microsoft Windows NT domain to Windows 2000 or Windows Server 2003, Windows 2000 Terminal Services clients may be repeatedly denied access to the terminal server. If you are using a Terminal Services client to log on to the terminal server, you may receive one of the following error messages:

Because of a security error, the client could not connect to the Terminal server. After making sure that you are logged on to the network, try connecting to the server again.


Remote desktop disconnected. Because of a security error, the client could not connect to the remote computer. Verify that you are logged onto the network and then try connecting again.

Additionally, the following event ID messages may be logged in Event Viewer on the terminal server:

Event ID: 50
Event Source: TermDD
Event Description: The RDP protocol component X.224 detected an error in the protocol stream and has disconnected the client.


Event ID: 1008
Event Source: TermService
Event Description: The terminal services licensing grace period has expired and the service has not registered with a license server. A terminal services license server is required for continuous operation. A terminal server can operate without a license server for 90 days after initial start up.


Event ID: 1004
Event Source: TermService
Event Description: The terminal server cannot issue a client license.


Event ID: 1010
Event Source: TermService
Event Description: The terminal services could not locate a license server. Confirm that all license servers on the network are registered in WINS\DNS, accepting network requests, and the Terminal Services Licensing Service is running.


Event ID: 28
Event Source: TermServLicensing
Event Description: Terminal Services Licensing can only be run on Domain Controllers or Server in a Workgroup. For more information, see Terminal Server Licensing help topic.


This issue may occur if a certificate on the terminal server is corrupted.



This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: 322756 How to back up and restore the registry in Windows

To resolve this issue, back up and then remove the X509 Certificate registry keys, restart the computer, and then reactivate the Terminal Services Licensing server. To do this, follow these steps.


Perform the following procedure on each of the terminal servers.

  1. Make sure that the terminal server registry has been successfully backed up.

  2. Start Registry Editor.

  3. Locate and then click the following registry subkey:

  4. On the Registry menu, click Export Registry File.

  5. Type exported-parameters in the File name box, and then click Save.


    If you have to restore this registry subkey in the future, double-click the Exported-parameters.reg file that you saved in this step.

  6. Under the Parameters registry subkey, right-click each of the following values, click Delete, and then click Yes to confirm the deletion:

    • Certificate
    • X509 Certificate
    • X509 Certificate ID
  7. Quit Registry Editor, and then restart the server.

  8. Reactivate the Terminal Services Licensing server by using the Telephone connection method in the Licensing Wizard.


    If you activate the Terminal Services Licensing server using the Telephone option, the licensing server uses a different form of certificate.