Comment 77 for bug 193970

what also works for me is this:

if killswitch is enabled (wifi off) nm-applet will disable the "[] enable wireless" menu entry
turning killswitch off should enable wifi, but the status led is still off, and no access points are shown in network manager
right-clicking on nm-applet "[x] enable wireless" is now activated. disabling it and then enabling it again, should bring up the status led and after some seconds all available networks.
no need to modprobe/rmmod in a terminal

be careful though… i had some kernel panics when enabling/disabling wifi