Computer-driven currency traders are learning that sometimes you just have to go with your gut. Big currency hedge funds like FX Concepts LLC and Ikos are tweaking, and in some cases overriding, computer models they blame for a disappointing performance this year. These models, which tell traders when to buy and sell based on factors such as market trends and economic reports, sometimes require weeks' worth of data before they spit out the right trading strategy. That wait has proved a liability lately as a series of sudden and unexpected events have whipsawed the euro by cents at a time, saddling some firms with ... (full story)