The August 2003 blackout was likely caused by a computer glitch:
A previously-unknown software flaw in a widely-deployed General Electric energy management system contributed to the devastating scope of the August 14th northeastern U.S. blackout, industry officials revealed this week.
The bug in GE Energy's XA/21 system was discovered in an intensive code audit conducted by GE and a contractor in the weeks following the blackout, according to FirstEnergy Corp., the Ohio utility where investigators say the blackout began. "It had never evidenced itself until that day," said spokesman Ralph DiNicola. "This fault was so deeply embedded, it took them weeks of poring through millions of lines of code and data to find it."
The flaw was responsible for the alarm system failure at FirstEnergy's Akron, Ohio control center that was noted in a November report from the U.S.-Canadian task force investigating the blackout. The report blamed the then-unexplained computer failure for retarding FirstEnergy's ability to respond to events that lead to the outage, when quick action might have limited the blackout's spread.