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Did you also use "knoppix keyboard=de xkeyboard=de"?

Have a look at http://knoppix.net/wiki/Cheat_Codes → ### Language/Country ###

You are using a wrong file! Either you or another person deleted the origin. The origin looks like this example (from 7.4.0 / german version):
# KNOPPIX 7.4 isolinux/syslinux boot config

DEFAULT...

Have a look at → Micro-Remastering

This isn't the origin file!