This same thing happened to me a couple of weeks ago. I called VZW and asked them what I should do. The only option was a Master Reset of the phone. It solved the problem. Of course, I lost everything that wasn't synced to my PC, including email account setup parameters. So you'll have to go back in and set everything up, as well as reload any files you may have had on the phone.

You get to the reset selection by Start > System Tools > Master Reset

Hope this helps,
Jim