After installing 12.04 on my vaio laptop everything was OK. But when I disabled the WIFI from the Ubuntu menu the wifi showed an message that it was turned off with the hardware switch.

The weird thing: there is no hardware switch to turn off WIFI, neither does the BIOS have options for disabling the WIFI.

Doing a “rfkill list all”:

After some searching I found a solution:

Now your WIFI should work again.