Ok, so in case it is any help at all, I try to give information about my problem as well (which seems to resemble the ones you have). I am definitely a newbie which does not understand what happens at all, so I am sorry if information is misleading or whatnot. Please let me know if you want me to try anything else / give you more information.

I have kubuntu 7.10, linux 2.6.24-19 on my Thinkpad T61p (core 2 duo T9300) with the Intel(R) Wireless WiFi Link 4965AGN driver for Linux, 1.2.0. In the beginning everything seemed to be working just fine. Then after a while I had problems finding networks, more and more so. To my surprise it seemed that moving the lid sort of helped (the antenna is here), so I was worried if this was a hardware problem (still don't know). From what I understand now, it seems to me that it's more likely a driver issue. After I have get a connection, I have no problems losing the connection again or similar. Also, what I discovered recently, was that placing the laptop just next to the router while trying to connect helped a lot. I would also like to add that the problem seems random, sometimes it's hopeless, sometimes it's almost non-existing. And, at work I have no problems finding and connecting to network until now anyway. The difference between home and work is that at home there are about 10 different access points discoverable, and there's no encryption at work. A last comment is that one of the available access point is a N-network. For some reason I often find this without finding any other network. This is why I try to connect to this network in this example (I don't know if the driver/utilities support N network yet, but that's a different story anyway, that's not urgent in any way for my part). As a "conclusion" it seems that the "thingy" hangs after a failed attempt to connect to the a.p. (this is also true when it tried to connect to b/g network and failed). Using the kill switch stops the dmesg output.

I attach a dmesg output that hopefully could give you some kind of information. A short summary:

booting the machine
dmesg output

[    0.000000] Initializing cgroup subsys cpuset
[    0.000000] Initializing cgroup subsys cpu
[    0.000000] Linux version 2.6.24-19-generic (buildd@vernadsky) (gcc version 4.2.3 (Ubuntu 4.2.3-2ubuntu7)) #1 SMP Wed Jun 4 16:35:01 UTC 2008 (Ubuntu 2.6.24-19.33-generic)
...
[   27.925629] Bluetooth: RFCOMM socket layer initialized
[   27.925645] Bluetooth: RFCOMM TTY layer initialized
[   27.925649] Bluetooth: RFCOMM ver 1.8

iwlist wlan0 scan --> nothing new in dmesg, does not find any network(!)
ifconfig wlan0 down
ifconfig wlan0 up

[  178.228974] ADDRCONF(NETDEV_UP): wlan0: link is not ready

iwlist wlan0 scan --> find N-network, nothing new in dmesg, does not find any other network(!)
knetworkmanager to connect

[  201.257703] NET: Registered protocol family 17
[  202.005125] wlan0: Initial auth_alg=0
[  202.005134] wlan0: authenticate with AP 00:00:00:00:00:00
...
[  204.271979] iwl4965: Not a valid iwl_rxon_assoc_cmd field values
[  204.271983] iwl4965: Invalid RXON configuration.  Not committing.


dmesg -c
dmesg

[  219.591122] wlan0: authenticate with AP 00:00:00:00:00:00
[  219.591673] wlan0: RX authentication from 00:00:00:00:00:00 (alg=0 transaction=2 status=0)
...

After knetworkmanager says connection failure
dmesg -c
dmesg

[  226.288370] wlan0: authenticate with AP 00:00:00:00:00:00
[  226.288923] wlan0: RX authentication from 00:00:00:00:00:00 (alg=0 transaction=2 status=0)
...