Oct 1 16:25:11 pc kernel: wlan0: associated
Oct 1 16:27:21 pc kernel: iwlagn 0000:03:00.0: Microcode SW error detected. Restarting 0x82000000.
Oct 1 16:27:21 pc kernel: Registered led device: iwl-phy0::radio
Oct 1 16:27:21 pc kernel: Registered led device: iwl-phy0::assoc
Oct 1 16:27:21 pc kernel: Registered led device: iwl-phy0::RX
Oct 1 16:27:21 pc kernel: Registered led device: iwl-phy0::TX
Oct 1 16:28:54 pc kernel: wlan0: disassociating by local choice (reason=3)
Google reveals several bug reports for this error for many popular Linux distributions: Ubuntu, Fedora, Gentoo, Arch...; it was also reported on Intel's bugzilla. The bug has been known for months but it looks like it's not apparent what's its root cause. The problem occurs under high traffic volume or after long inactivity. The connection doesn't work anymore, but it is not reported as such by NetworkManager or iwconfig. To get it working again,you have to reconnect with NetworkManager or reload iwlagn module.
It seems there are two workarounds, I've tested both of them and both worked for me:
- set "swcrypto=1" option for iwlagn module using modprobe.conf
- use ndiswrapper driver, that is, the wrapper for MS Windows driver.
Judging from the changelong for RC of kernel-2.6.32, there is a buch of fixes related to Intel wireless drivers (and iwl4965 in particular), let's hope the problem will be gone when 2.6.32 is finally released.