You may want to see if the module (tulip) for the card is is loaded with lsmod if it is in use you will see a 1 beside it.
Code:
tulip                  38560   1
Also check in the file /etc/network/interfaces it should look like this for a DHCP connection:
Code:
# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

# The loopback interface
# automatically added when upgrading
auto lo eth0
iface lo inet loopback


iface eth0 inet dhcp
if the line for the dhcp is not there add it by editing the file as root then also as root /etc/init.d/networking restart to restart the network with the new settings. You may also want to check the file /etc/resolv.conf for your nameservers example file:
Code:
search wolf
nameserver 192.168.1.10
nameserver 192.168.1.34
The search line for your domain is not necessary and you only need one namserver line for it to resolve IP address.

Also from a console window you could check the boot messages to confirm the card gets initialized during boot dmesg | grep eth0 should return a line with your card in it.