IPHONE 4S wifi become grey, after updated 6.0.1

My Iphone 4s have an error for WIFI.

After my phone updated 6.0.1, and wifi suddenly become grey and its adress indicate N/A.

Some people said it is caused by software update(6.0.1)

Pls tell me the reason, because it is very inconverient.

Many people have the same problem as me.

By the way, pls tell me when the software will be updated to 6.0.2

Thanks in advance.