You don't mention whether you tried to set up your network card using the Knoppix network card configuration utility. I find that, using Knoppix 5.1.1 (you don't say which release you're using), it does *not* work if you use DHCP. You might find some helpful details in this posting
http://www.knoppix.net/forum/viewtop...965&highlight=
or maybe the other postings referenced therein.