Remember last year the satellite that was supposed to be snatched from the air with helicopters equipped with special hooks- but smashed into the desert? It turns out it's an example of how things can go wrong even after being tested to death.
The probable cause is that two g-switches (Accelerometer switches.) were installed upside-down. Before you blame the guy who assembled the PCB- he followed the design to the letter. In other words- Lockheed supplied the faulty design.
NASA link one
NASA link two
It would seem to be fairly easy to devise a non-destructive test to verify that the circuit would fire when hit with force from the appropriate direction.