The Terminator (Schwarzenegger) kills John Connor, is reprogrammed, and sent back in time to insure his survival on Judgement Day. But he warns Connor that he will kill him in the future, insuring that Connor has no reason to trust him, thus making useless the fact that he'll get close enough to kill Connor and negating every event afterwards. Doesn't this create the paradox like Back to the Future describes? You're making future events useless by current actions.
PS-this is what the alphabet would look like if Q and R were eliminated