Fortinet SSL VPN Client and Ubuntu 12.04
You probably have the Ubuntu 64 bit version (at least it was my case). If so, just install the following package:
sudo apt-get install libgtk2.0-0:i386 xterm
For those who are using 64bit ubuntu 14.04 (after clean install you have to install these packages)
sudo apt-get install libgtk2.0-0:i386 libsm6:i386 libstdc++6:i386 xterm
I have had it to work. However it wants you to accept a License Agreement which it will try to open in xterm. So make sure that xterm has been installed:
sudo apt-get install xterm