I tested Cinnamon 1.4 and it appears to work work fine.

Perhaps this bug report needs to be retitled to state that only newer
versions of cinnamon that are affected?

This is just a VM I setup for the specific purpose of testing Cinnamon
compatibility with X2Go.

More details are below. Note that GLX is enabled, and I ran the
"Custom Desktop" command: gnome-session-cinnamon . "cinnamon2d" was
not present in this older version of Cinnamon.

----

I have the GLX extension enabled on my test system
(/etc/x2go/x2goagent.options has the line to disable GLX commented out)
- Linux mint 13 maya (based on Ubuntu 12.04 precise) 64-bit
- All latest level 1, 2 and 3 OS updates installed.
- cinnamon version: 1.4-UP3
- Cusstom Desktop specified in x2goclient: gnome-session-cinnamon
- x2goserver & x2goserver-xsession: 4.0.1.15-0~847~ubuntu12.04.1
- nxagent & x2goagent: 2:3.5.0.27-0~446~ubuntu12.04.1

I've attached the contents of my .xsession-x2go-errors file.

Note the following session files::
batmin@mint-m /usr/share/gnome-session/sessions $ ls
cinnamon.session  gnome-classic.session  gnome-fallback.session

batmin@mint-m /usr/share/gnome-session/sessions $ cat cinnamon.session
[GNOME Session]
Name=Cinnamon
RequiredComponents=cinnamon;gnome-settings-daemon;
IsRunnableHelper=/usr/lib/gnome-session/gnome-session-check-accelerated
FallbackSession=gnome-fallback
DesktopName=GNOME

batmin@mint-m /usr/share/xsessions $ ls
cinnamon.desktop  gnome-classic.desktop  gnome-fallback.desktop  ssh.desktop

batmin@mint-m /usr/share/xsessions $ cat cinnamon.desktop
[Desktop Entry]
Name=Cinnamon
Comment=This session logs you into Cinnamon
Exec=gnome-session-cinnamon
TryExec=/usr/bin/cinnamon
Icon=
Type=Application
X-Ubuntu-Gettext-Domain=cinnamon

batmin@mint-m /usr/share/xsessions $ cat /usr/bin/gnome-session-cinnamon
#! /bin/sh
exec gnome-session --session cinnamon "$@"