I had the same bug on Debian Squeeze 6.0.2.1, I solved by installing the package firmware-iwlwifi_0.28_all.deb (squeeze) or the package firmware-iwlwifi_0.33_all.deb (sid) and deleting from the /lib/firmware folder, the firmware iwlwifi-5000-5.ucode, so the kernel will read the latest firmware ie: iwlwifi.5000-2.ucode
Federico Fiore
