My model # A1355 AirPort Time Capsule has stopped communicating via Wi-Fi with my iMAC. It still works with my wife's PC.

Open System Profiler.. or whatever name it now has in ML. (system information).. and open the system report and go to the Network Wifi.. you will see if the wireless has failed. Or it might just be not installed.

It must be a fairly old unit to be using Atheros card.. they have mostly used broadcom for a fair while. Although I am not as sure of the iMac.

schubb1948 wrote:

This helped. It said "Status: Network Service Inactive" Any idea how to make it active? The iMAC does not recognize any network and seems to have lost all of the networks which were previously used and saved.

If you cannot even turn on the wireless.. it is either not working or damaged.

Do you mean ethernet is also not working?? Your first post said ethernet was ok.

Look up the error.. but to me, it will need lots of low level commands and changes.. that suggest that the OS has corrupted itself.. but much more likely the wireless is simply dead.

See https://discussions.apple.com/thread/3196661?start=0&tstart=0

Although it is lion I imagine you have done an upgrade from Snow Leopard to Mountain Lion..

The best test would be a clean install of Mountain Lion.. Install to a USB disk if you don't want to mess up your current boot.. and set that as the boot disk.

If it still fails, then the card is faulty.. it is probably not worth the effort to fix it.. !!

A work around.. buy a second hand express or extreme.. very cheap now if you search ebay, craiglist ?? and use it as wireless extend to the TC... and plug your Mac into it by ethernet. Voila,, network again by wifi.. and probably better than the internal card ever was.