I'm not sure about this, but you didn't type the whole cheat as

knoppix vga=normal screen=1024x768 or screen=1280x1024

did you? I meant that the screen cheat could be either 1024x768 or 1280x1024, not both. This could be insufficient caffeine on my part.

Try: knoppix vga=normal screen=1024x768. If that doesn't look right, try knoppix vga=normal screen=1280x1024

Let me know if either works.