I recently had reported installing x2goserver on a totally new server machine and the x2goclient on a totally new client machine both running Ubuntu 12.04 beta 2 and the fact that when trying to start an x2go session it would always indicate "running" then immediately fail/terminate.
I've found out the following.
After adding the x2go PPA for debian/ubuntu
sudo add-apt-repository ppa:x2go/stable
sudo apt-get update
In the past all I've had to do on the server was install x2goserver
sudo apt-get install x2goserver
then edit /etc/ssh/sshd_config and enable ChallengeResponseAuthentication to YES
ChallengeResponseAuthentication yes
However, with the new x2go versions apparently that is NOT they only module that needs to be installed.
On the server you now also must install x2goserver-xsession
sudo apt-get install x2goserver-xsession
My best guess is that this was introduced when the new x2go versions implemented the ability to published apps on the x2go server without having to install any sort of desktop environment on the remote "server" machine.
After installing the x2goserver-xsession the x2goclient now successfully creates a remote desktop session with one caveate... I've had to setup the remote server for ssh automatic login
If using Ubuntu refer to: https://help.ubuntu.com/community/SSH/OpenSSH/Keys
If I do not do this then the login to the remote server will always fail due to some ssh failure but I am not sure if its the client or server side that fails but that is another problem to figure out later. At least I can get a remote desktop now.
I'm not sure if the above change was documented anywhere on the x2go wiki but I will check and add it if it doesn't exist yet.
Brian