My wife has an iPhone 3GS which has been on the stock iOS4 software for the past few weeks. All of the sudden today (maybe yesterday actually too), she can't send or receive text messages. I verified that my iPhone is fine (trading texts with friends who are on AT&T, T-Mobile, and Sprint). I even called AT&T and they just said they have no idea why and I should check with Apple. I also tried to completely restore as well as restore as new iPhone and no luck. Anyone else ever experience something weird like this? Thanks!