"You've taken on a design challenge and come up with a solution that's been widely admired and won you accolades. But a year or so later, you realize you made a mistake. There's something horribly wrong with your design. And it's not just something cosmetic — a badly resolved corner, some misspaced type — but a fundamental flaw that will almost certainly lead to catastrophic failure. And that failure will result not just in embarassment, or professional ruin, but death, the death of thousands of people.