[basilray]

I have seen my phone do this once or twice. It usually happens when I am trying to send a text or something that uses data at the same time.

Have you tried disabling everything but the cell radio to see if there is a conflict? If that is the case, it sounds like something that needs to be addressed by Sprint.

Also, just as a test, have you tried deleting a contact and re-saving that contact to see if that has any effect? It could be an issue with your contacts, especially if you are restoring them after a backup.