Knoppix is a mix of testing, unstable and even stable I think.
If you remember which packages you got with synaptic you could check from which tree they were with: apt-cache policy packagename
Looks to me like you got some from testing and now it wants to downgrade the ones depending on them also to testing.
What happens with: apt-get -s -t unstable install packagename_you_installed and_another_one