So, to cut in short. This problem is known and caused by recent changes in Linux kernel and use of undocumented functions in Witcher2 -
http://steamcommunity.com/app/20920/discussions/0/620700960252675402/
https://github.com/KillaW0lf04/The-Witcher-2-Issues/issues/89
in Kernel 3.17.7 there is some strict checks for "set_thread_area" was implemented to fight off CVE-2014-9322, CVE-2014-9090 security issues but current Witcher 2 version is not ready for this and crash on start.
Linus Torwalds made some patches to enable Witcher 2 to work https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/tls&id=83b0849b38a3badaada90807ab8d7b3a4c31b9f6 but these patches is not mandatory and its up to distribution maintainer to choose to allow Witcher 2 run OR provide better security for known exploitable hole.
So, you can easily predict which task will be chosen - security for all or game for some.
I hope CD Project is not expecting that Linux distributions will fix bugs in Witcher 2?

P.S. Current latest kernel in Ubuntu 14.10 is 3.16.0-30. Kernel 3.17 probably will be in upcoming Ubuntu 15.04.

Let's hope for a patch before the new version becomes popular. Unfortunately CD Project Red is propably knee deep into getting Witcher 3 released, so my guess is a solution for this issue will have to wait.

Thanks for bringing this up Redfern. It might be a good idea to let the official Witcher support know.

Hope so. It was wrong idea to use undocumented functions in undocumented way in first place. With source code i guess CD Project can get it fixed more or less easy (easier then compiling your own kernel)

Good news, thanks for the info.