Given that part of the standard advice given to novelists is "you must hook your reader from the very first sentence", and there are indeed authors who manage to craft opening sentences that compel one to read more*, hooking the gatekeeper from the first sentence and keeping them hooked long enough seems doable even for a human playing the AI.
( The most recent one that I recall reading was the opening line of The Quantum Thief*: "As always, before the warmind and I shoot each other, I try to make small talk.")
Oh, that's a great strategy to avoid being destroyed. Maybe we should call it Scheherazading. AI tells a story so compelling you can't stop listening, and meanwhile listening to the story subtly modifies your personality (e.g. you begin to identify with the protagonist, who slowly becomes the kind of person who would let the AI out of the box).
Update 2013-09-05.
I have since played two more AI box experiments after this one, winning both.
Update 2013-12-30:
I have lost two more AI box experiments, and won two more. Current Record is 3 Wins, 3 Losses.