I'm going to disagree with several of you in this thread. "Thinking outside the box" is not just "management-speak", but can be good advice in many cases, forcing you to consider whether you are operating with assumptions that might be invalid.
I'm a long-time fan of crossword puzzles, and have been working the New York Times puzzle every day for nearly the last forty years. The editors of these puzzles, Eugene Maleska (until his death in 1993) and Will Shortz, go out of their way to be tricky, especially in the Thursday, Friday, and Saturday puzzles. If you aren't open to different interpretations on a clue's meaning, the puzzles will be difficult or impossible to work.
Some examples:
Clue: "Group getting its kicks"
If you interpret this to mean people who are enjoying some activity, you might guess HEDONISTS, or some other synonym. The actual answer is CHORUSLINE.
Clue:"Expert savers"
If you're thinking along the lines of PENNYPINCHERS or some other synonym that implies being economical, you're guilty of "thinking inside the box." The answer here is GOALIES.
These aren't the best examples -- they're just a couple of clues I picked out of Saturday's NYT crossword. The point is, when we communicate with each other, how we interpret what we hear is often different from what the speaker really intended. If you approach the problem thinking that there is only one possible meaning, you might be operating with flawed assumptions.