Hi, I live overseas and recently bought an unlocked iPhone 3GS that I had hooked up to iTunes. Everything worked fine and my sim card from this country was valid. When I disconnected it and reconnected it, a sign popped up saying i could upgrade to iOS 4 or something, so I clicked update. Then, it starting backing up my iPhone and restoring it, but when it was finished and I reconnected it with iTunes, a sign came up saying that my sim card is not valid. Why would it say that when it had accepted it in version 3.1.3? Now, I was thinking maybe if i just re-inserted my sim card again it would work, but i'm having difficulty getting it out of its hard case. Is that what the problem is, or is it worse? I just tried downgrading it back to version 3.1.3 from the iOS 4 version, restoring it to its "Factory Settings" but it still gave me the same message: that my sim card isn't valid. please help!