Erratic WPA wireless connection (ipw2200, wpa_supplicant)

[Pablo Ramella <pnramella@gmail.com>]

Hello
I'm using Debian squeeze. Over what seems like the past year, I've had
trouble getting my Thinkpad T42 to maintain a stable connection to my
home access point. It sometimes takes forever to associate, or loses
the connection apparently randomly. I only use a single access point
with WPA, configured in /etc/network/interfaces. The file currently
looks like this:

$ grep -v '^#'  /etc/network/interfaces

auto lo
iface lo inet loopback

auto eth1
iface eth1 inet static
  address 192.168.20.3
  netmask 255.255.255.0
  network 192.168.20.0
  broadcast 192.168.20.255
  gateway 192.168.20.1
  wpa-ssid 0024A56F0670
  wpa-psk 8118744*...snip, this line has to be OK else i'd _never_ associate*

A few other specs that might be relevant:
$ lspci -nn |grep Wire
02:02.0 Network controller [0280]: Intel Corporation PRO/Wireless
2200BG [Calexico2] Network Connection [8086:4220] (rev 05)

$ dpkg -l '*firmware*'
--snip headers--
ii  firmware-ipw2x00                           0.28
       Binary firmware for Intel Pro Wireless 2100, 2200 and 2915
ii  firmware-linux                             0.28
       Binary firmware for various drivers in the Linux kernel
(meta-package)
ii  firmware-linux-free                        2.6.32-30
       Binary firmware for various drivers in the Linux kernel
ii  firmware-linux-nonfree                     0.28
       Binary firmware for various drivers in the Linux kernel

When the connection is down, I usually see this in /var/log/daemon.log:
Mar 21 11:56:18 sioux wpa_supplicant[944]: Trying to associate with
00:24:a5:6f:06:71 (SSID='0024A56F0670' freq=2417 MHz)
Mar 21 11:56:18 sioux wpa_supplicant[944]: Associated with 00:24:a5:6f:06:71
Mar 21 11:56:18 sioux wpa_supplicant[944]: WPA: Key negotiation
completed with 00:24:a5:6f:06:71 [PTK=TKIP GTK=TKIP]
Mar 21 11:56:18 sioux wpa_supplicant[944]: CTRL-EVENT-CONNECTED -
Connection to 00:24:a5:6f:06:71 completed (reauth) [id=0 id_str=]
Mar 21 11:56:24 sioux wpa_supplicant[944]: CTRL-EVENT-DISCONNECTED -
Disconnect event - remove keys
Mar 21 11:56:24 sioux wpa_supplicant[944]: Trying to associate with
00:24:a5:6f:06:71 (SSID='0024A56F0670' freq=2417 MHz)
... and so on, repeated.

I'd appreciate any tips; I have no idea how to solve this. I also
can't tell what causes the connection to be lost.
I have also tried using network-manager a bit, and that doesn't seem
to make a difference.
Pablo