You really shouldn't try dist-upgrade on Knoppix. If you proceed, you will almost certainly break stuff big style. See the top of your /etc/apt/sources.list for a safer (no guarantees) way to proceed. The issues are because (most) Knoppix releases use stuff from all the Debian trees (whicjh is why some of us reciommend Kanotix for a HD install).

Anyway, mine reads:

# /etc/apt/sources.list for Knoppix
# If you want to do a "full upgrade", you should first
# upgrade the Packages from Debian/unstable (KDE & Co.)
# before doing a (dist-)upgrade for Debian/testing.

# See sources.list(5) for more information, especialy
# Remember that you can only use http, ftp or file URIs
# CDROMs are managed through the apt-cdrom tool.