First and foremost, it's not likely the keypads. If it were the keypads, it would only be a single key or two within an often used octave. This is not the case.
Best guess is that one of the connectors has either become loose, or one of the boards has gone south.
First, try a Master Reset; Function/Utilities/System Reset, and place a check mark in all boxes. If you have lots of custom settings, save them to either the HD or a floppy disk before doing the reset.
If the reset does not work, the next step is to open the keyboard and check the ribbon connectors going to the keypad boards. If this doesn't solve the problem, then it's likely that one of the boards has gone south, which is a factory authorized service center repair job.
Good Luck Bill,
Gary
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Travlin' Easy