I've had this Korg K25 for years; I know old and small, but I'm asking because I suspect it's not because of this particular keyboard (k25) - I've never had any trouble and today all of a sudden, it will not sound Eb, G or B natural anywhere on the keyboard in any octave. It's on all vst instruments I choose, and when I use the mouse to sound those notes they are there - I'm thinking it's got to be some midi thing because why those particular notes in every octave? Any advice from anyone as to why all of a sudden these particular notes don't sound? It's a mystery to me - thanks for any help.