Have you tried to connect a cable that goes to one of the working laptops to the NOT working computer. If you have did it work. Have you tried the cable from the NOT working computer to a working one to see if it works on that one. After that if the computer works with the other cable then it must be the original cable that is faulty. If the computer that does not work still does not work then I would check your setting on the computer for the network cables.
Hope this helps. sorry about the way its worded