yoel-
No, Mr. Till... there is no contradiction here.
Saul DID smite all of the Amalekites from Havilah to Shur. But there was a
tour group of Amalekites on a Carnival Cruise and when they got back, saw
that all of their kinfolk from Havilah to Shur had been slaughtered, they
fled southward to Egypt, went to the Amelekite neighbourhoods of Cairo, got
the people all stirred up, and they came back to take revenge on the
Israelites who had slaughtered all of their relatives.
But the Amalekites did not go north of Shur, because when they got there,
the sultry and surly prophetess Shirley, she of the talking ass*, came out
to warn them and that they not should surely not enter lest they surely die
and they said "Sure, surly Shirley the sultry seeress, surely the Lord is
in this place", and it is called thus (Shur) to this day! (with a few minor
spelling alterations due to Hebreo-Jurassic ARCHAISMS).
But Shirley was a double agent for the Israelites, sent to stall the
Amalekites, lest they disrupt David's cavorting with Batsheva. When David
had finished, God sent him to Shur to fulfill the prophecy "Thou shalt
SHURLY die" Genesis whatever).
There is no contradiction here.
* see Numbers 22:21-33 and Pink Flamingos