Karliah may not be waiting for you at the stone at the beginning of the quest. This is may happen if you come across the nightingale stone before this quest. You can fix this glitch on PC by going to the quest marker and typing "player.placeatme 0001B07F" into your console.
Quelle: http://elderscrolls.wikia.com/wiki/T...stored_(Quest)
Da hats noch weiter bugs und lösungen aufgelistet... vll hilfts