It sounds like the setup is having a hard time finding a driver to use with your card. I don't know the wording but you can specify to use the VESA generic driver and set the resolution at the boot prompt. That way it uses what you specify and skipps the detection stage. I will try to edit this post once I have found the code to use. I have seen it on other posts in this forum.

(later) I Found a thread that may be of use.

http://www.knoppix.net/forum/viewtopic.php?t=4276

try at boot prompt:
knoppix vesa, 1024x768 (if not try the same but with 800x600)
or
knoppix vga=normal