In addition to this, I just realised that when I use 'fglrxinfo' I get this:
display: :0.0 screen: 0
OpenGL vendor string: Mesa project: www.mesa3d.org
OpenGL renderer string: Mesa GLX Indirect
OpenGL version string: 1.2 (1.5 Mesa 6.2.1)
Apparently, they should be ATI and not Mesa, is that correct? How can I fix this? And what are the possible causes?