Incidentally, I interviewed a guy yesterday and we whiteboarded a real problem we had encountered last week. He couldn't solve the problem we presented and really didn't even try to dig in much. I was surprised how unwilling he was to dig in so I started asking him about his own environment and tried to get him to describe other problems he's solved and how they might relate. He couldn't really do it even with that being so open ended. At the end of the interview I came away with the impression he was just turning knobs at his other jobs and didn't have much of a chance to think for himself. In this case more enthusiasm would have gone a long way for him because if he could have shown me mastery over the things he did know I would have been willing to teach/train him on the many things he didn't know yet.