I'm not an expert as far as Knoppix/Linux goes, but I've had Knoppix freeze up on me in the past and gotten a similar error when I tried to restart. After searching myself with no luck I went to trial and error, and found that if you boot without your home directory, create a knoppix config file of your "Personal configuration", then restart and specify both your corrupted home file and the config file at the boot prompt, it will 'repair' your home file and start up correctly.