Although Corsair generally has a reputation as a top-notch supplier of computer power supplies, it seems they didn't get things quite right with their "Builder" series CX*** models. They supply good clean outputs but there are several accounts of early failures.
I have personally come across two faulty units with similar symptoms - one 500W and one 430W unit. They turn on with light loads with all voltage rails within specs but cannot boot up a computer even with all drives and add-on cards removed. The first one was a customer's that died within 6 months and the second was DOA. Has anyone here found a common design flaw and/or know of a source for the schematic?