I gave Jessie a try in VirtualBox and here is what I found:
One of the first things I did was add my user name to sudoers(this may have been part of the problem if you were trying to set up a service install .. i.e. start automatically ... as users are not allowed to use sudo by default in this version of linux).
Open a root terminal by typing terminal in the Activities search window:
For the installers I did a right click on them and selected Open with gdebi.
I entered my identity info but removed the check in start automatically since I was testing and didn't want anything to start automatically.
The FAHClient installer terminal log did show an error status code 1 but didn't explain the cause of error. However, the client did install. I then created a sub-folder called fah in my home folder, switched to it and typed FAHClient. The client paused because there was no config.xml file in that folder. I should have copied config.xml from /etc/fahclient to my /home/username/fah first. My first connection attempt to the assignment server did time out for some unexplained reason but after the time out (~2 minutes) everything worked as expected.
FAHControl did install using gdebi with no problems and when I first ran it there was a message saying my identity was not setup and asking for the info which I did enter again. After doing so the client downloaded a work unit and commenced processing.
The client appears to be running fine and the work unit is showing progress in the log.