go to Menu,
System, Administator, Network
enter your root password
You will see the nic information. (if it is not there then the device was not recognised)
If it is there,
does it say active?
double-click on the etho line. A detailed pop will show the settings.
make sure all the settings are correct - like active device when computer starts.
If this does not work, make sure the dhcpclient service is running.
All things being normal it should work.
Do the Math