Jan 2004: “The Mars Exploration Rover Spirit suffered a debilitating anomaly that prevented communication with Earth for several anxious days. With the eyes of the world upon us, the anomaly team used each scrap of information, our knowledge of the system, and sheer determination to analyze and fix the problem, then return the vehicle to normal operation.”
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http://www.cs.princeton.edu/courses/archive/fall12/cos109/mars.rover.pdf
Via http://space.stackexchange.com/a/9181
which addresses a different postmortem: In July 1997 the Mars Pathfinder computer locked up due to priority inversion, and again it was possible to patch the software and recover the mission.
Both these answers contain good pointers to further materials.