I have had the same sliding door problem .  Remove the interior panel and
you will find that one or more of the wires connected to the automatic
door lock system at the front door latch have come of.  Just squeeze the
clip and replace to it's connection.  Not complicated if you know where to
look !  Took me a few weeks before I stumbled across it.

Cheers

Frank

-- 
              *  Frank Condelli  *  Almonte, Ontario, Canada  * 
                      *  ad793@Freenet.carleton.ca  *
                          MGB's and LIONEL Trains