I was asked how to reproduce this bug.
I got the problem from a customer who uses a Ubuntu 12.04 laptop as a client (I don't know which client version) and a server with Debian Squeeze and an up-to-date X2go server.
I have reproduced it then myself with my personal computer as a client (Debian Squeeze 64-bit with some backports) and a computer of another customer as server (Debian Squeeze 32 bit, up-to-date X2go server). There I could reproduce the bug. Both fullscreen and in a window.
What I did is login on the server, change the keyboard settings in Gnome to deadkeys, and test it in the keyboard-settings-window.
On non of this computers I use this line in sources.list: deb http://packages.x2go.org/debian squeeze main So no "heuler".
With regards, Paul van der Vlis.