I am running Ubuntu 14.04 and had not had problems with the wifi until a couple of days ago. I have tried numerous help posts, most of which with similar fixes, and nothing worked.
It started after I switched to using 'Auto ethernet' in order to download things faster, and when I tried switching back to wireless, I found that the hardware switch for the wireless has been disabled, and I can no longer connect wirelessly.
Hitting the actual switch doesn't do anything.
sudo rfkill list all returns:
0: phy0: Wireless LAN Soft blocked: no Hard blocked: yes
lspci | grep Wireless returns:
10:00.0 Network controller: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection (rev 02)
sudo rfkill unblock all does nothing and neither does:
sudo rfkill unblock wlan
Nothing in the hardware changed, I only noticed the problem after I installed another distribution on another partition, when I unplugged it from the ethernet.