My co-worker and I both got our new iPhones today at the same time. They screwed me all up (http://forums.macrumors.com/showthread.php?t=517232) but he was just changing from a first gen iPhone to the 3G. So they swapped his sim card for him and told him to activate it with iTunes later. We've been sitting here at work all day trying to get the phones to activate with iTunes with no luck just like everyone else. To see what people were hearing when they tried to call us, we called the numbers from the office phone. His unactivated phone started ringing and after answering the call is *magically* working! Long and short: if your upgrading from the first iPhone and have the same sim card, try calling the phone and see if it starts working without activation!