keyboard not typing 8 i k comma

i have two dell latitude CPx laptops.  both have a problem of not being able to type the   8, i, k, and the comma.  i took the keyboard appart and reconnect it and worked for a little, but back to the problem again.  this has happened to both keyboards on my two latitudes cpx.  sometimes they work, sometimes they don't (intermittantly).  would appreciate some help, thanks   manny