Click on the network icon.
Select manual configuration and input your password.
On the "Connections" tab you should see Wired Connection and under that
it will say Address: dhcp.

Click on the Properties button in the Connections tab. Do you have under
configuration "Automatic configuration (DHCP)"

Click on the DNS tab.
Do you have any DNS servers listed?


If all that checks out try:
sudo /etc/init.d/networking restart

I also have:
sudo dhclient