The only knoppix-specific part is the fact that knx-alsa caused the problem. There are a few knoppix packages that can make upgrading more of a pain. The only ones I can think of right now are knx-alsa and openoffice-de-en. But you can get the same error messages in a pure debian system...especially when you're doing a dist-upgrade and such. Forcing it to overwrite will fix it generally though.