iPhone 4S OSX 7.1.2 Wifi switch greyed-out (disable) Apple sent a replacement 4S last month: I have used the wifi w/o problems until today.

I have tried:

1) Rebooting the device several 

2) Bouncing airplane mode

Questions:

A) Are there any settings (other than airplane mode) that will disable wifi?

B) Are there any diagnostic procedure that can ID root cause of wifi disabled?
If the Wifi switch is being displayed as greyed out that means that there is a hardware problem with the Wifi modem in the device. I had faced this with my device and Apple replaced it under warranty, I would suggest take the device to an Apple store and they should replace the device as you get 3 months support on replaced devices even if it was a paid replacement.

P.S: Rebooting, Resetting or any other changes can not fix this issue as it is a hardware issue, the earlier you go to the Apple support the better.