It says-

Sorry, sudo must be setuid root.

But I am root and I'm using su knoppix. I thought I could set a root passwd as you normally would and so I used passwd root. Then this trouble started and I can't become knoppix anymore. What should I do to fix it?

Should I maybe replace /etc passwd passwd~ shadow.passwd and sudoers with the original files from the cd? Any other files that might have been changed when I ran passwd root?