(install utilities as nessesary)
Error: couldn't find RGB GLX visual or fbconfig
Error: couldn't get an RGB, Double-buffered visual
reason: you does not use nouveau driver but fallbacking to vesa. Yep, vesa _could_ render DVI images of high quality, and even support dual monitor configuration. But not an opengl of any kind.
So, main reason of problem is one of following:
1) No nouveau driver (kernel module: check lsmod|grep nouveau)
2) No xorg.conf.
Minimal xorg.conf from nouveau wiki should help:
Section "Device" Identifier "n" Driver "nouveau" EndSection
3) Check if no nvidia traces are in system.
4) check if libGL and libGLU are in system.