I'm using smoothwall behind a hughes.net satellite internet modem. It took alot of research through the smoothwall forum to get it to work.
Long story short I can't use dhcp
I didn't mean to imply that it was a cd/dvd issue, just differentiating between the two versions of Knoppix without using the same label over & over.
I used k3b to burn the iso & I beleave that does an md5 test before it burns.
I have a how-to to fallow on the usb install & I'm willing to give it a try. http://www.knoppix.net/wiki/Bootable_USB_Key
Bottom line I wanted to point out another possible reason for the problems had by the other posters in this thread.