Sun's back in the red again after five profitable quarters and five years in the red following the dot.com bust. The March quarter turned sour on it, starting, it said, with the first week in March when the channel stared reporting a drop in sales, a miasma that spread to its end-user business as the month progressed. It blamed the US economy, where business was down 10%, some of it traceable to smaller businesses and the government, it said. (Former Sun CEO Scott McNealy runs Sun Federal.)