You might want to view another "thread" that was going on in General Forum, they had the same issue, and message, you report...

I can't install Knoppix on my HD

Even though the initial issue was in installing Knoppix v3.6, the resolve was from a Knoppix v3.4 system, and yes, the resolve was by myself, as well...

To summarize, it appears the installer has problems if the format isnt already in place, and the resolve is to "manually" do that format before the installer is used. cfdisk only partitions the disk, it does not format it ( as a side note ) -=- considering this resolve is 1 for 1, currently, it cant hurt to see if it goes 2 for 2