Comment # 19 on bug 1053115 from Stefan Dirsch

Thanks! Now I remember what happened. You once have updated TW from Mesa to
Mesa+libglvnd. At the same time the nvidia driver was installed manually. With
uninstalling it, NVIDIA's installer restored these libGL.so.1.2 files, which
now no longer are part of Mesa. But they are preferred over the ones from
libglvnd (libGL.so.1.0). So they need to be removed manually. Unfortunately. If
you could add this information to 'NVidia the hard way wiki page', this would
be great!