What do you mean that it does not work. It can be a driver related problem, so try in step-by-step.
Check your kernel version. Check if it supports Via-Rhine network card. If you use some liveCD, check that there is a kernel module loaded for your card (lsmod, there should be via-rhine module loaded). Check your PCI devices list (/proc/pci, lspci). If your network card is configured (ifconfig), can it get any IP address from a DHCP server?
There are many layers of networking and you did not give any clues fo us where to start. Do not give up so easily :-)
Examine boot time logs with dmesg, etc, etc...
And there is another thing if everything stuck: http://www.scyld.com/driver_updates.html