Here's something I figured out (because one of my systems has a wonky cd drive)

First, get an iso image of knoppix and put it on your usb flash drive.

Boot with knoppix, and use the bootfrom parameter to switch to using the iso knoppix image on the flash drive.

"knoppix bootfrom=/dev/sda1/knoppix51.iso" will find an image named knoppix51 on the flash drive and run knoppix from it.

You can also use wildcards like "knoppix bootfrom=/dev/sda1/k*.iso"

I think this saves a lot of wear and tear on your cd drive.

The magic of this solution is that you don't have to worry about making your usb flash drive bootable,
just boot from the cd and run off the flash.

You must boot with the same knoppix version on the cd as the one on the flash drive.