Originally posted by Anna B. the Greek:
... "The ring, Harry. Marvolo's ring. And a terrible curse there was upon it too. Had it not been — forgive me the lack of seemly modesty — for my own prodigious skill, and for Professor Snape's timely action when I returned to Hogwarts, desperately injured, I might not have lived to tell the tale. ...
If Snape had wanted Dumbledore dead all along, why proceed with 'timely action' that kept him alive?