I recently purchased an iPhone 3GS and have been loving everything about it. I was upgrading from the original iPhone so this is a huge upgrade for me. One nagging problem has to do with WiFi. I had this problem on my old iPhone and it seemed to follow me to my new one. At home whenever I turned on wifi on the iPhone it would work for one application but when I closed that app, it would disconnect from the wifi. It was very frustrating.
Well I finally resolved this issue and I want to pass along my findings. I found the answer in a MacRumors Forum. I basically had to reset my network settings to get this fixed.
1). Click on the settings button on your iPhone
2). Click the General button.
3). Select the Reset Menu.
4). Select “Reset Network Settings” (This will not reset your whole iPhone, only the WiFi settings).
5). This may take a minute and your iPhone will reboot and you should be right as rain.
Hope that helps everyone.