How do I fix a lost wi-fi connection & "no wi-fi hardware" warning?
I randomly lose internet connection, and cannot reconnect. I either get a no network detected warning or a warning that I do not have wi-fi hardware. The problem might be related to a recent upgrade to Lion.
Go under the Apple in the upper left hand corner to "about this Mac" > more info > Network > Airport and see if your card is being seen. If not reseat the card, if it still fails, replace the card. Here's how to do it: Installing MacBook Core 2 Duo AirPort Card
According to which machine you have, here are the cards: Relevant parts
MacBook Core 2 Duo Santa Rosa/Penryn 802.11n Airport Extreme Card
MacBook Core 2 Duo 802.11n Airport Extreme Card
802.11n Airport wireless internal card — 17 available at 79.95 each.
802.11n Airport wireless internal card for Santa Rosa Macbooks — 7 available at 99.95 each.