False Alarms in the Nuclear Age (2001)

More on the training tape incident here, with photos of the hardware and operators: http://nsarchive.gwu.edu/nukevault/ebb371/

According to press reports, based on Pentagon briefings, a NORAD staffer caused the mistake by mistakenly loading a training/exercise tape into a computer, which simulated an "attack into the live warning system." This was a distortion because it was not a matter of a "wrong tape," but software simulating a Soviet missile attack then testing NORAD's 427M computers "was inexplicably transferred into the regular warning display" at the Command's headquarters. Indeed, NORAD's Commander-in-chief later acknowledged that the "precise mode of failure ? could not be replicated."

Fascinating, but frightening.

Eric Schlosser's 'Command & Control' is a fascinating and very readable look at nuclear accidents and almost-accidents. Recommended if you're interested in this area.