Boge,
It seems that your graphics card is NOT detected by knoppix properly and it is using a "generic" driver just to be able to display the UI.This happened to me in a similar manner with my savage card.Try using fb1024x768 at boot up.
Alternatively you can remaster knoppix like I did and insert the proper driver for you graphics card like I did.(http://www.knoppix.net/forum/viewtopic.php?t=11114)