Als Alternative für einen guten X-Client unter Windows habe ich X-Ming32 http://www.osalt.com/x-win32 ausgewählt.

Voraussetzungen auf UNIX:

• By default remote x-windows (port 6000) is disabled in Ubuntu. Now one easy way around this is just to use ssh to login with port forwarding like such:
  $ ssh -X host
  This will set the DISPLAY variable automatically and any X program you run will be automatically tunneled back through the ssh connection.Otherwise we’re going to need to enable it. Here’s how:
  
  1. Go to System->Administration->Login Window (or run gdmsetup as root)
  2. Under the security tab uncheck „Deny TCP connections to Xserver“
  3. Now we have to restart gdm which will kill our Xsession.
  # kill -HUP cat /var/run/gdm.pidor if you prefer to edit /etc/gdm.conf by hand, make sure there are no overriding settings in /etc/gdm.conf-custom. Under the security section change DisallowTCP to false.

  Unfortunately we cannot use gdmflexiserver, only a gdm restart will work.

•  if you have /etc/gdm.conf-custom then modify the disallowtcp setting, if not just modify it in /etc/gdm.conf. Then run:
  # /etc/init.d/gdm restart