This article at a blog called Billo The Wisp is important if true. Turbine gearbox failures apparently happen typically after 5-7 years rather than the 20 years that we are normally led to believe wind turbines last for. Moreover, their failure can be completely catastrophic, leading to the destruction of the whole turbine.
Billo has discovered that a group of US scientists has been commissioned by Washington to look into the problem, but they don't seem to have come up with anything since they started work in 2007.