Although I don't have this card, my google searches tell me that you want to load the via-rhine module. I'm not sure if this module is compiled into your kernel by default so try this from a shell (after su'ing to your root account)
insmod via-rhine
you'll want to make sure that the following line is inserted into /etc/modules.conf
alias eth0 via-rhine
If this doesn't work, you'll probably need to recomile your kernel. There are many threads in this forum which cover the topic and you can also read the Kernel HOWTO over at
http://tldp.org
All the best,
Adam