I have a 1-year old unlocked, jailbroken iphone 3G running OS 3.1.2. Recently, I have had this problem where the 3G data connection will suddently stop working. In Safari I get a Cannot open page because Safari is not connected to the internet, in mail.app I get a Cannot get mail server connection failure, and then in other applications that require the internet, nothing loads. If I reboot my iphone or turn on airplane mode and then turn it off again, the connection works for a few page loads or email fetch cycles, and then the problem comes back again. Everything works fine over wifi, and at all times I can make calls and send and receive SMS. This problem occurs anywhere I have been in the city (NYC) since the problem started. Ive made done a number of things with the iphone over the past week before the problem started happening. I installed the app Byline, and I was playing with the SIM card and took it out and switched it with the SIM on my AT&T blackberry to see if the BB SIM would work in the iphone out of curiosity (it did not and I then put the iphone SIM back in). Right before the problem started, I removed my Gmail push/sync account and replaced it with an IMAP connection to Gmail, because I felt like the push access was taking a toll on my battery. I am not sure if this caused the problem, though, because it happens even after Ive deleted all email accounts. Ive searched a lot over the past day and have tried a number of things, none of which have worked: -- Deleting and reinstalling my Gmail account in a couple different ways and doing a number of things related to email (unlocking captcha on Gmails side, toggling SSH on and off, changing IMAP and SMTP ports, enabling and disabling push, etc.) -- Rebooting my iphone before and after trying various changes -- Removing, cleaning and reinstalling the SIM card -- Turning off 3G and EDGE connectivity, both through the Settings app and through SBSettings -- Reset network connections through the Settings app The one thing I have not yet tried is restoring the phone. Does anyone have any other ideas before I do this? Has anyone else experienced this problem?