open a program like Notepad... and let it sit.   See if characters are depressed.   Such as 5,1,  ect.    id say theres a short, faulty switch,  or ipac trouble. 
  try replacing the micros with new ones.  maybe they are the blame.
   ive seen a ghost only once in 32 years of life, and it was a very rare event.  even rare-er is a ghost that can actually interact with the physical world (poltergeist).  And if it was one of them, youd see the buttons actually depress.