HolgiB wrote:The question is though why Ubuntu (with Nouveau enabled per default) does NOT show such a behaviour
Probably because the version of kernel is different, the version of X.Org Server is different, etc. It's not just a question of whether one is using driver X instead of driver Y, it's a question of which versions of X and Y one is using, and which versions of the supporting software 'infrastructure' (X.Org etc.) one is using. I recently tried to help someone I know to get audio working in SL. Even I couldn't crack it, and I know SL quite well. So he switched to Ubuntu, which worked out of the box in every area with his particular hardware (the story could be completely the other way round on different hardware, as I can personally attest). The versions of most packages were different (less bleeding-edge in Ubuntu), the configuration files were different, the kernel version was different (less bleeding-edge in Ubuntu), the kernel configuration was different, the modules blacklisted were different, and so it goes on. It is like comparing apples and oranges.