I'd suggest using the forcedeth driver, I have an NF4 mobo and I use forcedeth and have found it's just as good as nvnet. Try running 'lsmod | grep forcedeth' to see if it's loaded. If it's not just modprobe it and then do this to bring a link up.
Code:
ifconfig # first just to check that eth0 isn't already up
ifconfig eth0 up
dhclient eth0