From Blue-IT.org Wiki
For Ubuntu there is a ppa available:
There is also an x2go portable-apps-client.
Reconnection a session gives you the following error:
The remote proxy closed the connection while negotiating the session. This may be due to the wrong authentication credentials passed to the server.
sudo apt-get remove --purge -y x2goserver x2goagent x2goclient rm -rf ~/.x2go* ~/.nx sudo apt-get install x2goserver
sudo apt-get remove --purge -y x2go* rm -rf ~/.x2go* ~/.nx sudo apt-get install x2goclient
Be sure you are using "16m-jpeg".