I upgraded my jailbroken iPhone3G from iOS 3.1.3 to iOS4 using RedSnow. As I could not get any phone connectivity after that, I decided to restore to default iOS4 and be un-jailbroken. That worked and I could call and receive calls using iOS4. However, I noticed that when I'm not connected to any wifi network, the 3G data connectivity is not working. I just cannot get access to the Internet when I'm away from wifi connectivity. Despite turning Network > Cellular Data to ON (as well as OFF) and Network > Data Roaming to ON (as well as OFF), nothing worked. My iOS is 4.0 (8A293) and my modem firmware is 05.13.04. Any advice on how to fix my problem? Thanks.