As I blogged a few days ago, my iPhone was unable to make outgoing calls although I could receive calls, even with 5 bars of signal. After restoring, resetting network settings, and making sure the SIM card was properly seated, I made an appointment and brought it into the Apple store today.
After the Genius did some tests and tried restoring the iPhone, he determined it was a hardware problem and gave me a new iPhone.
Getting a new iPhone meant I had to add the device ID and create a new development provisioning profile before I could use it for development in XCode.