Screen turns off when in a call

[CaliforniaPlaya]

Had the Evo for a couple of weeks. Starting last night, when I made a call the screen turns off as soon as the call is connected and there appears to be no way to make it come back on. Its not just the backlight, it is the screen. Even pressing on it where the buttons are (number, end call, etc.) has no response. As soon as the call ends (other end has to disconnect since I can't) and I hit the power button, it comes back on. I didn't install or update any apps that may be causing a conflict. I've restarted, tried turning GV off and that has no effect. Any ideas?

Thanks!!!