Have a look at: http://support.microsoft.com/default.aspx?scid=kb;en-us;323497
1. Start Registry Editor.
2. Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINESystemCurrentControlSetServicesTermServiceParameters
3. Under this registry subkey, delete the following values: • Certificate
• X509 Certificate
• X509 Certificate ID
4. Quit Registry Editor, and then restart the server.