Mensagem original de: David ,
Try looking in > About this Mac > System Report and look for the "WiFi" section. If you see something like "no hardware found" that means that your wireless card has become detached from your motherboard. You can open up the laptop and make sure the cable is plugged in. If you see information about your wireless card, then you may have some software which is blocking or turning off your wireless card. You'll have to google that or provide us with more information.