You would have to call a Janome dealer to find out that answer. It does sounds pretty messed up. I heard once that having a light shine on the screen will cause problems especially if there is a magnifying glass on it (burned a hole!).
Have you tried using the eraser end of a pencil to touch the screen with?
How does it sew out? Is the alphabet part the only problem with the screen? Can you use the other functions like arch words, rotate designs, etc.?
Good luck with it. I love my Janome.

That is easy to fix my dealer helped me over the phone.Go to Mode and go to the screen that you balance the machine by using the removeable thread holder and you touch the plus signs and when finished.It's done.I hope I explained it to be understood. I have a 300E