mitch - one last thing to take a look at - does the keystation have zone setups that perhaps persist, where there's a split keyboard setup that might be sending on different midi channels and whatnot?

I would take a look at the midi monitor I linked to - it should gather all the midi output - see if there is anything coming from the dead keys. If they are individual keys inside of a group, then I would say the thing is bad.

-Scott