Ok, this commands might help (I'm assuming that the cable is connected, interface is called eth0 and that there is a dhcp server somewhere on your network):

sudo ifconfig eth0 up

sudo dhclient

Strange... could you open your Terminal application as mentioned before and paste here the output of these commands (some were already mentioned, but bear with me :) ):

status network-manager

cat /var/lib/NetworkManager/NetworkManager.state

ifconfig

route -n

cat /etc/network/interfaces 

nslookup linux.com

dns is working... i know I've posted a lot of commands here, but the output hopefully will give the ppl in this thread a better insight on the problem...

perhaps examining the commands used in this script would help: http://www.ossec.net/wiki/Tweaking_OSSEC#Easy_uninstallation

If in the output of this command

cat /var/lib/NetworkManager/NetworkManager.state

you'll see that the networking is disabled, delete the NetworkManager.state file (and restart the service)

sudo rm /var/lib/NetworkManager/NetworkManager.state

sudo service network-manager restart

if your samba server is not accessible from the Internet try to delete or comment out these two lines from your smb.conf

interfaces = 127.0.0.1/8, 192.168.0.0/24

bind interfaces only = Yes

and restart the samba daemon (just a suggestion, may not help... for some reason your samba daemon is listening only on 127.0.0.1) ... btw, what is the IP of your server, for example the output of this command:

$ ifconfig

You can also run the nvidia xconfig tool (current xorg.conf will be backuped as xorg.conf.backup)

$ sudo nvidia-xconfig

reboot (or restart the x server), now the nvidia settings should run properly

$ sudo nvidia-settings