The problem is that libgl1-mesa-glx seems to be broken in some ways in vanilla Knoppix:
Code:
apt-get install --reinstall libgl1-mesa-glx
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libgl1-mesa-glx : PreDepends: multiarch-support but it is not going to be installed
E: Broken packages
I keep looking for a solution.
I hope the next Knoppix version will have this problem solved.