That message means you either have no graphics card, or Crystal Space (the 3d engine Planeshift uses) doesn\'t recognize it (probably because of bad/no drivers). Another highly unlikely possibility is that you have an ancient gfx card that only does 2d acceleration which doesn\'t help much for gaming.
look at your card manufacturer\'s website for updated drivers, or use windows update (if you are on windows)
For linux, it is possible that you are using MesaGL drivers... not sure how exactly to fix or change that, ask one of the linux gurus around here.
josePhoenix