IPhone :: 4S Can't Find Any Home Wifi Networks

I got a new iPhone 4S on May 15, 2012. It worked great at the AT&T store and connected to their secure wireless no problem. I spent 6 hours at home trying to get it to connect to my wifi network - it couldn't find mine or any of only 1 of the other 5 that my iMac can find. I have a Netgear WNDR3700 (the dual band n) router that the iMac, the Macbook, two TiVos and my old 3G phone connect with no problem - and all these devices except the iMac are downstairs in the opposite side of the house from the router. So...I reset my network settings on the phoneI turned wifi on and off again on the phoneI turned airport mode on and off again on the phoneI turned the phone off and restarted itI updated the firmware and the GUI on my routerI took off the security, walked up to the router until the phone was 3 inches away, and it found the network and connected. Safari worked fine on wifi. I walked 5 feet away and the wifi was gone. (The phone will find and connect to my neighbor's unsecured network, but drops the connection if I move more than 5 feet from where I picked it up.)I reinstated the WPA2 security, held the phone 3 inches from the router and connected via the passphrase. Signal dropped again at 5 feet away. I restarted the cable modem (just for kicks) and the router. I changed the router security keys. I added the phone's MAC address to the access list on my routerI did a factory restore on my router, changed the network names and passphrases.I took my phone to the gym, Starbucks and the Apple Store. It connected to the wifi and even made backups on iCloud. It lost the connection at the gym when I went upstairs, but it was still connected when I was outside in the parking lot, so who knows about that. At my Apple Store Genius Bar appt. - which the Apple support guy made for me after he'd been on the phone with me for an hour with no result - the guy immediately gave me A BRAND NEW PHONE. He said it must be a wifi chip problem and that they get about one of those phones a month. I thought, "Lucky me, I won the lemon phone lottery!" I switched my info to the new phone via iCloud while I was in the store and took my brand new phone home: it still sees no networks except my neighbor's and doesn't stay connected for more than 5 seconds. It makes no difference whether I remove the security or not - the phone absolutely will not find my network or any of the other 5 networks near my home.

Info:
iPhone 4S, iOS 5.1.1