This situation such as the one below came up in a hand last nite ( LC's Fun Tourney ), and as coincidence would have it, I saw a similar problem in the newspaper bridge column today.

You need  all 6 tricks in a suit to succeed in 3NT.  There are no transportation problems, but a common error is made.  The 10 is led to be run.... but is covered by a  stiff  honor  .    Now there is no recovery.  Down 1.

 

                               10 x

 

       9 x x x                                   K

     

                          A Q J x x x