Disklavier

Hi Wayne
I am having a similar adventure than your withe the disklavier radio  and my piano. In my case the piano is an used instrument bought in Italy recently (mpx1 about 10 yo which has the mkII xg system on it) . The instrument works fine and plays very nice... My nephew who went to Japan 2 monthe ago brought me back the DKC850 controller box (half the price than in France where I live); after having changed the main language of the unit to english I thought that was it. Until I decided to subscribe to the internet radio (4 days ago): since that I am stuck with the same issue you describe in your post: all is in japanese after D-RADIO is pressed and impossible to sign in it seems. I have written to musicsoft  and yamaha uk for explanation or help in making it work but no answer yet... I searched the web to find something and your post is the only one where I see that you are dealing with the same issue. Did you find a solution ? If not I will send you one when I find one ! 
I think it must have to do with the internal network adress or web adress the unit is using to get in contact with the radio server there must be a different one for the "english" users because also the number of channels available are only 21 as opposed to the 28 actually offered at musicsoft...

Thanks for any insights you may have

Alain