This is an issue when trying to access the IBM iAccess Key Database that holds all the certificate information necessary for using SSL.
Make sure you've run the updates.cubase.org for enabling encryption as well as the everyone permission to ensure all users can access the key database file.
Next you will want to access the IBM iAccess for Windows either through Control Panel or the Start Menu and go under the Secure Sockets option. Select 'Use default key database' if not already selected and open the 'Settings' window to select on 'Use Window's logon password'.
After this you should be able to sign into the secure print sessions correctly! If you're still having issues try re-creating the secure print sessions.