I purchased an iPhone 4 GSM new/sealed from an Apple Store in July 2010

and never needed to connect to multiple Wi-Fi networks until recently.

When I would go from a known Wi-Fi connection to another one,

I would need to go into Settings to reconnect each time.

I figured that I needed to replace the Wi-Fi antenna.

When I took off the back panel, I discovered that the 4.8mm Phillips screw

that grounds the Wi-Fi antenna is not present. So, you might want to first

check that the screw is there and properly secured.