Give us some more information
What operating system are you using?
What graphics card are you using?
Have you tried to upgrade the drivers of the graphics card? (can usually be found on the website of the manufacturer)
If you are on linux I can only think of either a driver problem, a misconfigured Xorg, or a globally installed version of CrystalSpace which is outdated and not compatible with planeshift anymore. If that is the case and you have downloaded the client from the main website (instead of building it from source) you should try to "unset $CRYSTAL" and try once more
For the case you are a windows or mac user I have to pass out.
Anyways, without more information we will only be able to speculate.
Greetings, Cebot