No WiFi on a system76 laptop after upgrade to 15.04

I just upgraded System76 Gazelle laptop to 15.04 and wifi no longer works.

It sees many networks and tries to connect to mine, but fails repeatedly (/var/log/syslog seems to indicate authentication failure, but the password in the /etc/NetworkManager/.../my-wifi is, of course, correct).

I tried rebooting both the laptop and the wireless modem.

I also tried Fn-F11 (which now turns on "airplane mode") with no results.

I also tried wired internet which is also ignored.

How do I restore the WiFi?

PS. Also http://ubuntuforums.org/showthread.php?t=2275442

Found an answer:

sudo mv /lib/firmware/iwlwifi-3160-12.ucode /lib/firmware/backup-iwlwifi-3160-12.ucode
sudo mv /lib/firmware/iwlwifi-3160-10.ucode /lib/firmware/backup-iwlwifi-3160-10.ucode

Reboot. Seems to be an issue with the firmware. After reboot I was able to connect again, so for me it is working.