I managed to go to Mexico on holiday, but since I going there I'm constantly getting the network lost message even when my phone is switching between 3G and 2G. I'm home now and I'm getting it over 20 times a day when I move about. It wouldn't Be so bad but if you're writing an email or SMS it stops the keyboard working. I've another iPhone for work that I took with me (on vodafone) and that isn't suffering at all. Is it worth a dfu restore to see if it can clear this message? I've attached the message so that you can see it.