When I try to run the demo (in windowed mode) via "launch_game" I get a "Segmentation fault". No more error messages.

Running Debian Linux 64bit, with Nvidia drivers.

Any ideas?

Does the config tool run ok, launched with launch_config?

Yes, that runs fine. I tried with or without fullscreen, with different resolutions.
In all tests the result is the same. The game itself crashes with the segfault.

Is there a log file that I can find somewhere to post it here?

Yes, there should be a log at yourhomedir/.running_with_rifles/, namely rwr_game.log and rwr_config.log. You could send them to me at pasi.kainiemi@modulaatio.com or make them available somewhere.

I have sent the log files to your email address.
Thanks.

I have the same problem on the same OS, with the full game, here is the log file:

https://gist.githubusercontent.com/jamesmcm/996d0ff92494fd4bc1b9/raw/6e0a6fd6e825947dfd761b230b318d9b89c84097/gistfile1.txt