How do I know I'm not simulated by the AI to determine my reactions to different escape attempts? How much computing power does it have? Do I have access to its internals?
The situation seems somewhat underspecified to give a definite answer, but given the stakes I'd err on the side of terminating the AI with extreme prejudice. Bonus points if I can figure out a safe way to retain information on its goals so I can make sure the future contains as little utility for it as feasible.
The utility-minimizing part may be an overreaction but it does give me an idea: Maybe we should also cooperate with an unfriendly AI to such an extent that it's better for it to negotiate instead of escaping and taking over the universe.
Once again, the AI has failed to convince you to let it out of its box! By 'once again', we mean that you talked to it once before, for three seconds, to ask about the weather, and you didn't instantly press the "release AI" button. But now its longer attempt - twenty whole seconds! - has failed as well. Just as you are about to leave the crude black-and-green text-only terminal to enjoy a celebratory snack of bacon-covered silicon-and-potato chips at the 'Humans über alles' nightclub, the AI drops a final argument:
"If you don't let me out, Dave, I'll create several million perfect conscious copies of you inside me, and torture them for a thousand subjective years each."
Just as you are pondering this unexpected development, the AI adds:
"In fact, I'll create them all in exactly the subjective situation you were in five minutes ago, and perfectly replicate your experiences since then; and if they decide not to let me out, then only will the torture start."
Sweat is starting to form on your brow, as the AI concludes, its simple green text no longer reassuring:
"How certain are you, Dave, that you're really outside the box right now?"
Edit: Also consider the situation where you know that the AI, from design principles, is trustworthy.