The wifi in my hp probook 4540s with ubuntu 14.04 not working with message "Device not ready"
$ rfkill list that showed me
phy0: Wireless LAN
Soft blocked: no
Hard blocked: no
rfkill unblock all and rebooted but the problem is the same.
I tried solution in this link but that made the wifi disappear from the list so i had to undo it.
Finally i opened from live CD ubuntu 14.04 and the wifi works so no hardware problems.