I updated to Xubuntu 15.04 today and was having trouble connecting to wifi after waking my laptop up from suspend. It would say the card was active, but it wouldn’t find any wireless networks in the scan.
This worked for me:
Edit or create
in the file.
This will unload the wifi driver before suspend and reload it after waking.
EDIT: Upon reading this: http://www.webupd8.org/2013/01/fix-wireless-or-wired-network-not.html, it’s probably best to run
sudo lshw -C network
to see what driver your card is actually running and unload that instead.