This month we're looking at a recent close call that you're probably not familiar with unless you're part of the shuttle program: a software anomaly that surfaced on the Endeavor's mission last November (STS-126, 11/2008). The anomaly did not endanger the mission — or the astronauts aboard — but it caught my attention because the software assurance process for the shuttle is so rigorous that we almost never experience software problems in flight. The root of the problem we're looking at lies in the evolution of software development conventions and practices. The way software programmers code has evolved over the last twenty years, and a recent software change caused old code that depended on old conventions to fail. This incident points to the dangers of using heritage resources and highlights the key activities that must accompany any modifications to heritage hardware or software. Thorough verification and validation, well-developed processes backed by careful training and obsessive anomaly investigation will help us successfully continue to use the resources we have developed over the last fifty years.