93 Silverado Radio Problem

I have a 93 Silverado with the AM/FM radio and remote cassette.  Suddenly, the radio has developed a problem.   It will turn on and show the station frequency and the volume "dots", but the volume and tuning buttons don't work and there is no sound from the radio.  I know that there are two parts to the radio, the control box and the tuner below the dash.  Has anyone else seen this problem and found a fix?  Is it a common problem?      

Have you been able to resolve the problem yet? I have the same problem in my 04 Sliverado.