Why do I get "Error Class Code: 2" when I am trying to register a system?

Issue

• rhn_register fails with following traceback:

[user@test.com]#rhn_register
Traceback (most recent call last):
  File "/usr/sbin/rhn_register", line 76, in <module>
    app.run()
  File "/usr/share/rhn/up2date_client/rhncli.py", line 74, in run
    sys.exit(self.main() or 0)
  File "/usr/sbin/rhn_register", line 58, in main
    ui.main()
  File "/usr/share/rhn/up2date_client/tui.py", line 1272, in main
    tui.run()
  File "/usr/share/rhn/up2date_client/tui.py", line 1220, in run
    win = self.windows[index](self.screen, self)
  File "/usr/share/rhn/up2date_client/tui.py", line 460, in __init__
    hw_activation_code = rhnreg._activate_hardware(self.tui.userName, self.tui.password)
  File "/usr/share/rhn/up2date_client/rhnreg.py", line 623, in _activate_hardware
    login, password, hardwareInfo)
  File "/usr/share/rhn/up2date_client/rhnreg.py", line 654, in activateHardwareInfo
    hardwareInfo, other)
  File "/usr/share/rhn/up2date_client/rhnserver.py", line 52, in __call__
    raise self.__exception_from_fault(f)
up2date_client.up2dateErrors.AuthenticationOrAccountCreationError: Error validating data at server:

Error Message:
    Invalid username/password combination
Error Class Code: 2
Error Class Info:
     Invalid username and password combination.