By Michael Riley and Ashlee Vance

Last June, three men squeezed inside a wind turbine in China’s Gobi Desert. They were employees of American Superconductor Corp. (AMSC), a Devens (Mass.)-based maker of computer systems that serve as the electronic brains of wind turbines. From time to time, AMSC workers are required to head out to a wind farm in some desolate location—that’s where the wind usually is—to check on the equipment, do maintenance, make repairs, and keep the customers happy.

On this occasion, the AMSC technicians were investigating a malfunction. They entered the cylindrical main shaft of the turbine, harnessed themselves to a ladder, and climbed 230 feet in darkness up to the nacelle, an overpacked compartment that holds the machinery used to convert the rotation of the blades into electricity. AMSC had been using the turbine, manufactured by the company’s largest customer, China’s Sinovel Wind Group, to test a new version of its control system software. The software was designed to disable the turbine several weeks earlier, at the end of the testing period. But for some reason, this turbine ignored the system’s shutdown command and the blades kept right on spinning.

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