This just happened to me last night,I placed my camera straight up towards the sky, to try and take a photo of the stars, and afterwards found it had the exact same problem of rear dial only moving between two shutter speed values. A lot of stress later, and almost a booking for repairs, I did the same thing and pointed the camera up to the roof, left it for a few seconds. The problem fixed itself. Try that? fingers crossed.
Pretty poor form Sony... especially for such an expensive camera.