NASA’s Mars Curiosity Rover fell into safe mode on 7 November but was successfully recovered three days later on 10 November. A recent upgrade of software (R11) resulted in a discrepency error after a data file was compared to the catalogue file, which, in turn, caused the unexpected reset. The problem was fixed by clearing out the catalog first before the R11 upgrade was implemented.
A more detailed description is available on spaceflightnow’s coverage.