MacBook (10.4.11) is unable to connect to wifi networks

Question

After updating with 10.4.11 (and the associated 2008-01 Airport update) a few months ago, my Intel MacBook has been unable to connect to my WPA2 network.
It will see my network name in the Airport drop-down menu, but fail to actually connect. The icon appears as if the notebook is rapidly connecting and disconnecting -- switching from five bars of signal to none and back again every few seconds. During this time, my MacBook never reports getting a connection, and all other devices on the network experience severe interference. I am able to connect to most, but not all, unsecured networks.
System Profiler reports my wireless card as AirPort Extreme (0x168C, 0x86), Firmware Version: 1.3.5 .
My router is a D-Link DGL-4300 with the most recent firmware. I am running an 802.11g network at 2.437ghz.
I've tried the following already, unfortunately without success:
. Switching to WPA from WPA2
. Removing all the preferred networks from my System Preferences and adding them back in again.
. Removing all the network info in my keychain and reconnecting to the network from scratch
. Switching the router to channel 11 (away from 6)
. Turning Interference Robustness on and off
. Manually specifying IP and DNS in my network settings, rather than DHCP
. Removing all other wireless devices from the network
Looking elsewhere on the net I find that a few other people seem to have this problem, and so far the only solutions I've seen are "roll back to 10.4.9" and "disable security on your home network," both of which are obviously untenable for security reasons.
The one (and only) WPA-secured router I am able to connect to is the Airport at my local Genius Bar, so they're unable to help me.
Has anyone else seen this, or have any ideas?
Thanks.

Answer 1

Well, I downloaded Pacifist and the 10.4.11 Combo Update. Pacifist verified the AppleAirPort and AppleAirPort2 .kexts on my drive as matching the ones in the package, but I forcibly reinstalled them anyway and rebooted. Still no luck -- now the network is back to the four-bars-no-bars death loop without even popping up the error dialog.
Luckily however Pacifist turned out to be the solution to the problem. A Google search on "Apple broke Airport" eventually led me to this thread with detailed instructions on rolling back to the previous version of the Airport driver, before the 2008-01 update: http://www.tuaw.com/2008/03/28/airport-extreme-update-2008-001-for-tiger/#c11509 504
I'll paraphrase it here for anyone else who has this problem:
Download the Airport Extreme client software version 2007-004
from http://tinyurl.com/yw3dnu.
Download and install Pacifist from www.charlessoft.com.
Delete /system/library/extensions/io80211family.kext
In Pacifist, open AirportExtremeUpdate2007004.dmg
and expand the sub folders until you can see the io80211family.kext
extract and direct it to extract the file to the
/system/library/extensions/ folder
restart
So now my Airport works again, though without whatever security they put in with 2008-01, I guess.
I suppose I'll have to embargo future OS updates until this gets straightened out, or else re-rollback the io80211family.kext after each one. I sure would like to talk to whoever wrote this update at Apple!
Thanks for your time, BD.