I have a similar problem with my laptop. I have Xircom PCMCIA network/Modem card. It worked fine with debian. The cardmanager recognises the card. But no network connection.

I modified my /etc/network/interfaces file as described.

e.g. auto eth0 etc.

When I type /etc/init.d/networking stop

it reports an error message with bootpc. I see that other people are having lots of problem with networking. When I was installing Knoppix to HD it reported an error with DHCP. It just could not find the PCMCIA network card.

BTW the networking did not work when I booted KNOPPIX from CD.
The same problem exists with HD install.