My Iphone Wi-fi does not work. I've tried almost everything...

Same problem. Suddenly WiFi stopped working. I live in Japan, have a locked, unmodified 4S purchased in the SoftBank network. (SoftBank had the original monopoly, but Au now carries iPhones as well.) After a week of frustration, I found this thread.

Long story short, I'm in my office, where I shut down my 4S and rebooted. No change.

Then I shut down, pulled the SIM card, and rebooted. Of course it couldn't connect to SoftBank, and wireless still did not work.

Shut down again, inserted the SIM card and rebooted. Voila! Wireless now works. Hopefully when I get home, my home wireless will be visible again as well.

There is hope!

Well, I spoke too soon. Got home, saw the home network briefly, but it disappeared again. So far, no luck.

Here's the follow up. I checked my purchase date, and noted it was January 14. Since it was the evening of January 9, I made a Genius Bar booking at the Apple Ginza store for the next day. Today (the 10th) I took the train in to Ginza (about an hour away) for my appointment.

After an initial description, and confirming the fact that I'm just barely within my one year warranty, I showed my assigned Genius the grayed out Wi-Fi button, he nodded, and said "just a minute."

Back he came with a new 4S, no other questions asked. I had done a full backup the night before going in to the store, so I got what I had thought might happen, a replacement.

The receipt I signed shows the value of the "repair" as 16,952 yen (US$192 at today's market rate), so I'm glad this didn't happen a month from now when I was past warranty. I did ask about a warranty on the new phone, and he said it does not extend an additional year from today's date, only 90 days. And I wouldn't be allowed to buy an extended warranty at this point. But my experience with Apple Customer Service has been excellent over the 24 years I've been an Apple product user, so I don't expect any problems.

However, this sudden loss of WiFi capability is troubling, and I still don't have any answers as to what is behind it. Perhaps a certain batch of 4Ss are susceptible to this problem when upgrading to iOS 6. But that's just speculation. Good luck to everyone else in this thread! If you're still under warranty and have this problem, I say run, don't walk to your nearest Apple Store, or take advantage of their mail in service.

You are such a lucky guy :-) I used to experience it last year. My iPhone 4S unlocked wifi just suddenly stop working. I tried by all means: reset setting, reset content and setting, a few time clean restore from iTunes, yet nothing happened. It's a hardware problem, kind of wifi modern crash, so if all of you my friends having this problem and have tried every possible solutions I mentioned, the only best way is to contact Apple as soon as possible. Make sure your phones are still valid for one year warranty (you can check it on Apple site). If Apple finds out it is the hardware failure and your phones are under warranty, they will send you a new (or refurbished one I think :-) at no charge both at all including the shipment fee! Good luck :-)