Actually, I experienced the same thing when Windows did an update for the wireless driver.
I found the solution to be in power management. I rolled back the driver and it still didn't work. Knowing that people had other complaints such as frame GPU drops due to power management, I looked on the power management tab of the device driver and unchecked "allow the computer to turn off this device to save power".
What I think is that the bios/board has an issue with power management in general. When you hit the switch and the machine also went into a power save mode, it shut down the card because of this setting. It could also be something with the ASUS power utility, but regardless, if you do this, you uncouple the power saving action from the wireless card.
I have to add, that just tried turning off the switch on the side after making this setting, and found that when I turned it back on, I also had to hit the FN +F2 key combo to re-enable the wireless. It does work consistently, where before, it took rebooting the computer before it would work again. To give ASUS credit, this is more of a Windows problem thhan a hardware issue. Windows 7 has some wierd power quirks that may not be that way in other OSs. The wireless card manufacturer makes their own drivers, so it's dificult situation.