A few days ago my phone kept restarting. So I followed the instructions I found here to reload the OS on my phone.
Now I can get to main screen, but my phone will not connected to ATT. Sometimes when I search for the network it restarts the phone. Other times it just times out and says "no service."
I replaced the battery and sim card (which I tested and works in another phone) and still not working.
You may need to re-send your service books and re-register your HRT. You can send the service books using the Email Setup Wizard. To re-register your HRT, Options / Advanced Options / Host Routing Table / Register Now
Assuming you had data service before the problem started, then it sounds like you need to call your carrier and tell them what's happening, including the response you get when you try to register. It doesn't sound like there's anything you can do on your end.
Posted from my CrackBerry at wapforums.crackberry.com