In network situations, when every PC is not working, the problem typically isn't a matter of incorrect settings and the next step would be to power cycle the P.O.E. device.  If it is a single PC connected directly to the wireless equipment, try restarting the PC first and see if the connection comes back.

One ethernet cable goes to your PC or router, the other goes to the integrated radio/antenna, and the last cable is for power.  If the Internet is down for all computers that should be online, unplug the power from the device and wait ten seconds.  Plug it back in, give it 30 seconds, and see if the connection is restored.  There should be a light letting you know that the device is indeed receiving power.

If your connection doesn't come up after that, try power cycling your router like you did with the P.O.E. device (if you have one, it's a box that networks your computers together).  If you do not have a router, simply restart your computer.