Sorry I think I cannot help you. But I used usb keyboards (both usb directly or via PS2 adaptaters) with knoppix without any problem.
by the way you should provide informations about your hardware: your computer's model, your keyboard. Did you try with another keyboard ? etc.

If you get any error message you must copy it (for this specific problem I suppose knoppix just starts probing scsi without telling anything about your keyboard).