After upgrading via sysupgrade for a few releases, I have had to cold boot to get dhclient athn0 working on an ar9280 in client mode.
Since my latest upgrade to a snapshot of Jun 17 kernel #275 with the previous kernel being from Jun 2nd #237. I seem to have to cold boot after running ifconfig athn0 down and then back up, where I'm *fairly* sure that I didn't need to before that Jun 17th upgrade. ifconfig debug mode shows the wireless handshake completing 4/4. Yet dhclient can't establish a link until cold booted. A warm reboot does not resolve the problem. Has anyone else seen this or can reproduce it? I'll try a sysupgrade in the meantime but I'm not sure there has been any code changes in areas that could resolve it.