Rather an old news item but amusing nonetheless.
It seems a bit of a bollock was dropped on a joint venture to produce a Mars orbiter; one engineering team using metric units while another used imperial units for a key spacecraft operation.
Result? One lost craft for NASA, costing $125 million!
I loved the statement:
"People sometimes make errors. The problem here was not the error, it was the failure of NASA's systems engineering, and the checks and balances in our processes to detect the error. That's why we lost the spacecraft."