Comment 23 for bug 327431

It seems this problem can be avoided by thus who configure the network in the old way, using /etc/network/interfaces, instead of using NM. There may be many reasons for this, mine is to have network going up without needing a local user to log in, because I often use SSH remote sessions.

So, in the wlan0 configuration made as usual, I added a pre-up configuration:
pre-up ifconfig wlan0 up

So the problem could be related to a WPA configuration sometimes starting with a wlan0 still down.

I don't know if NM users can handle this easily but if someone from ubuntu want to take into account this concern that makes hardy so unstable under the widely used intel wifi since the beginning (more or less depending on kernel iterations)... I hope it could help.