Disklavier

I am brand new to this group and have just had a new and worrying problem on my Mk IV.  Firstly I confess that I haven't used my disklavier for quite a long time (6 months?) and now I find that it won't play in acoustic mode.  If I put it in quiet mode it plays fine (although no keys are pressed), and in acoustic mode, the keys won't move and no sound comes out (obviously).  The pedal function works perfectly and the pedals merrily go up and down without any music sounding.  I have tried everything - shutting down, completely depowering, rebooting the controller.  The 'key' button on the controller is continuously greyed out and when I restart the controller I get the error message 'key drive is not recognised'.  
Has anyone got any ideas at all?
Thanks