Ubuntu – WiFi soft-blocked by rfkill on startup

I have a small Acer Revo PC with Ubuntu 14.10 that I'm configuring to run as a portable media center.

I'm trying to set it up as a WiFi access point so that I can control XBMC/Kodi with Android devices via an app. This works fine so far.

However, I'm having trouble with the WiFi being soft blocked by rfkill on every startup.

• I tried unblocking it in /etc/rc.local (rfkill unblock wifi) but this doesn't work. Whatever is causing rfkill to block WiFi probably happens after rc.local is finished running.
• If I SSH into the PC fast enough after a reboot, I can see that WiFi actually works for a couple of seconds and then gets blocked. I can see the network on my smartphone as well, but it disappears shortly after showing up.
• I found the file that supposedly stores the rfkill state: /var/lib/rfkill/saved-state. Changing the line to phy0 0 or phy0 1 doesn't solve the problem. Also the file doesn't seem to change at all, so whatever stores the state doesn't work.
• I tried removing the upstart scripts for rfkill (/etc/init/rfkill-[re]store) – no improvement.

What worked for me was the following line in rc.local:

sh -c "sleep 10 && rfkill unblock wifi" &

But this is a crappy workaround, I have to disable the AP and DHCP services from auto-starting and start them "manually" in rc.local after unblocking WiFi.

What causes rfkill to block things at startup? How do I disable this?