Considering what it's involved, Mars Rover Curiosity's mission has been going really well. Staggeringly well. But that couldn't last forever. The rover has hit its first real road bump with a gnarly computer failure that's going to delay all the science-ing for at least a week.
On Wednesday of this week, one of Curiosity's two on-board computers became corrupted, and started sending odd commands back home. And after investigation by the Curiosity "anomaly team" the decision was made to switch over all important computations from the A computer, to the back-up B. And on doing so, the rover promptly locked up into safe-mode.