Wifi doesn't work after hibernate but DOES work after suspend

Try sudo killall NetworkManager, as suggested in Network devices unmanaged after resume from hibernation in Ubuntu Gnome 13.10 . It works fine for me!

This issue seems to be caused by bug #1184262 . It is not related to the networking as such, but to power management.

The workaround I found was to create a file with: sudo gedit /etc/pm/sleep.d/10_resume_network and paste the following:

#!/bin/sh
#Tell Network Manager that resume was successful

case "$1" in
       thaw)
         nmcli nm sleep false
         ;;
esac

Then, save and close the file and enter sudo chmod +x /etc/pm/sleep.d/10_resume_network.