I went through similar grief with my soundcard, which now works fine following a "kludge" with alsaconf. I was getting error messages identical to yours.

The biggest problem was the effect of aRts... on the whole setup. I get lots of error messages from it, but can't uninstall it. If I try to remove it, Kpackage lists every bit of software on the machine and says it will uninstall all of that if I remove aRts... It's still there, but the kludge gets round it From what I've read elsewhere, the Knoppix sound problem is very machine and soundcard specific: my P600 and Creative SB16 can be got to work with Knoppix 3.8.2.