Comment 106 for bug 621265

After testing Intel 3945 on Ubuntu 10.10 & Ubuntu 11.04, I can confirm the issue still exists with WPA2 Routers.

I finally only got it working on Guadalinex V.7, a very nice ubuntu based distro.

Info:

lsb_release -rd
Description: Guadalinex V7
Release: 10.04

uname -a
Linux miguel-laptop 2.6.32-25-generic #45-Ubuntu SMP Sat Oct 16 19:48:22 UTC 2010 i686 GNU/Linux

dmesg | grep 3945
[ 0.283945] alloc kstat_irqs on node -1
[ 13.679017] iwl3945: Intel(R) PRO/Wireless 3945ABG/BG Network Connection driver for Linux, 1.2.26ks
[ 13.679020] iwl3945: Copyright(c) 2003-2009 Intel Corporation
[ 13.679090] iwl3945 0000:03:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[ 13.679104] iwl3945 0000:03:00.0: setting latency timer to 64
[ 13.744577] iwl3945 0000:03:00.0: Tunable channels: 13 802.11bg, 23 802.11a channels
[ 13.744581] iwl3945 0000:03:00.0: Detected Intel Wireless WiFi Link 3945ABG
[ 13.744718] iwl3945 0000:03:00.0: irq 32 for MSI/MSI-X
[ 14.365564] phy0: Selected rate control algorithm 'iwl-3945-rs'
[ 18.731716] iwl3945 0000:03:00.0: firmware: requesting iwlwifi-3945-2.ucode
[ 18.941682] iwl3945 0000:03:00.0: loaded firmware version 15.32.2.9
[ 40.565706] iwl3945 0000:03:00.0: Microcode SW error detected. Restarting 0x82000008.
[ 40.565728] iwl3945 0000:03:00.0: Error Reply type 0x00000000 cmd REPLY_TX (0x1C) seq 0x0000 ser 0x00000000

What also helps:

Put Router in 54G only mode.
Set Beacon interval to 10ms.
Set DTIM interval to 10ms/5ms.