How do I edit this file so apt-get doesn't get broken after an update and a few installs!

BTW, I'm using KNOPPIX 3.4, clusterKNOPPIX 3.4 and QUANTIAN 0.4.9.6 on debian knoppix-installed PCs. I can't get update or install to work at all in clusterKNOPPIX or QUANTIAN. Anyone know how to fix that?

TIA,
AJG