Comment 4 for bug 602210

I had problems with Wifi after suspending. Try this after resuming to see if it helps:

sudo killall wpa_supplicant

wpa_supplicant will respawn.

If it works you can automate this for every suspend by creating a file such as: /etc/pm/sleep.d/99fixwifi.sh

I found parts of the following solution here:
http://fooninja.net/2010/09/02/how-to-fix-wifi-after-suspendresume-in-ubuntu/

But I modified that solution to include killing wpa_supplicant like so: