Can't register a RHEL server to Satellite via Proxy

Issue

• Get an error when attempting to register a client system to a Satellite via an RHN Proxy

  [root@server  ~]# rhnreg_ks  --activationkey supercoolactivationkey --serverUrl http://rhnproxy.org/XMLRP --force
  An error has occurred:
  Internal Server Error
  See /var/log/up2date for more information
  [root@eagle ~]# tail -20 /var/log/up2date
  Internal Server Error
  [Mon Dec  6 18:11:20 2010] up2date
  Traceback (most recent call last):
    File "/usr/sbin/rhnreg_ks", line 216, in ?
      cli.run()
    File "/usr/share/rhn/up2date_client/rhncli.py", line 65, in run
      sys.exit(self.main() or 0)
    File "/usr/sbin/rhnreg_ks", line 90, in main
      rhnreg.getCaps()
    File "/usr/share/rhn/up2date_client/rhnreg.py", line 280, in getCaps
      s.capabilities.validate()
    File "/usr/share/rhn/up2date_client/rhnserver.py", line 156, in
  __get_capabilities
      self.registration.welcome_message()
    File "/usr/share/rhn/up2date_client/rhnserver.py", line 50, in __call__
      return rpcServer.doCall(method, *args, **kwargs)
    File "/usr/share/rhn/up2date_client/rpcServer.py", line 275, in doCall
      raise up2dateErrors.CommunicationError(e.errmsg)
  up2date_client.up2dateErrors.CommunicationError: Error communicating
  with server. The message was:
  Internal Server Error