A Windows virus hit the display consoles in the control room of the
Australian national electricity grid, presumably leaving the managers
bind to the system status. Luckily, system administrators had
Linux-based systems for development that could be swapped out for the
disabled Windows machines. It seems as much of a failure to properly
maintain the Windows machines as a failure of judgment in using a
virus-susceptible OS for mission critical systems, but it's fun
schadenfreude fodder for Windows haters.

Source: http://www.osnews.com/story/22289/Linux_Saves_Aussie_Electrical_Grid/