Mac Forum / General / Hardware / November 2007

Erase the drive and reinstall the operating system. If known wireless
networks still don't show up, your card or antenna most likely has
become disconnected or defective.

Could be any of the above, or a problem with the antenna (e.g. the
connector with the Airport card has worked loose, or the antenna itself
is broken).

From the way you worded the problem, I take it that you have tried it
with more than one wireless network, so the problem is definitely with
your laptop rather than your base station.

A starting point would be to go into System Profiler and click on
Airport Card under the Network heading. Does it show details about the
card or say "No information available"?

In the latter case, your computer doesn't think it has Airport. That
could be a software or hardware problem, but it may help to narrow down
the scope of potential issues.

If the Airport card information is displayed, then it may be a different
class of software problem or a hardware problem.

One way to eliminate a software problem would be to boot from another
system (preferably a freshly installed one) and see whether the Airport
works properly there. Do you have an external hard drive or another
computer with a compatible operating system?

There isn't a lot you can do to "misconfigure" an Airport card on the
client side. If you can't see any networks listed in the Airport menu
then there is something wrong with the software or hardware.

You can control which networks it will connect to, and if your wireless
network is not broadasting its SSID then you wouldn't see it listed in
the Airport menu; if the computer's copy of the network name and
password is scrambled then it would not be able to connect to that
network.

I've occasionally had problems where the auto connect mechanism
misbehaves (but manual connect is OK). I've usually fixed this by
purging my list of preferred networks in System Preferences > Network >
Airport, and the correpsonding password entries in Keychain Access.

It might be helpful for further diagnosis if you can provide more
details about your laptop: which model is it ("Model Identifier" from
the "Hardware" page in System Profiler is a reasonably good indication
of exactly which model you have, but the general model and speed may be
sufficient), and which version of Mac OS X are you running?