Macbook wifi stopped working

Given that nothing has changed in our office network I was surprised that this morning my macbook simply fails to connect to our wifi.

We have several windows laptops and one macbook. All of the windows machines are connecting fine but when trying to connect with the mac i merely get a 'connection timeout' message.

So far I have:

- Restarted the macbook and the router
- Removed the network from the preferred list and re-added it
- Changed the wireless channel
- Changed the SSID
- Changed the password

Nothing of the above has worked though again all windows machines connected without problems.

I finally changed the security protocol from WPA to WPA2 and this let me connect - for all of a few minutes before disconnecting itself.

I'm stumped..... I don't seem to have any other options. Does anyone have any ideas??

Since most things external to your Macbook work fine...and if you didn't change any settings from the last time your Macbook connected to this network...the problem could be that something inside your Macbook has failed.

- Nick

It gets stranger - I took the macbook home and it connected perfectly to my home network as normal.

It seems that the only issue is with my mac and my office network even though every other machine etc works fine.....

The only things I am thinking are:

- something interferring with the MAC wireless connectivity in my office (would it be possible that it would not affect any other machine??)
- a somehow corrupted file in the MAC relating to this network (how would I know and what can I do about it?)

A little more testing and it seems this is a security issue. If I remove all security from the wifi the mac will connect fine. Add any form of security (WEP, WPA, WPA2) and it fails....

hmmmm

Possibly a corrupted keychain file or entry. The Apple suggested resolution to this problem is as follows:

The following is a quote and hint from the OS X hints forum feedback. (Run by MacWorld Mag)

*************

The Genius Bar at the Apple Store helped me solve the problem. We opened Library » Preferences » SystemConfiguration, and trashed the entire contents of that folder. We also deleted all locations in System Preferences » Network, and recreated the location Automatic. Finally, we rebooted.

*************

I strongly suggest making a backup of these files and folders prior to trashing them. Or, move them somewhere that would allow them to be reinstated easily.

Did all that - no change.
I also connected another AP to the router with WPA encryption and it joined first time....

I could assume there was a compatibility issue if it had never worked but it has worked fine up to now.