on a psu using a multimeter will only give you the no load voltage. i beleive your issue is happening under load, and i'd put money on it being either the 12v rail or the 5v from the pcie. depending on what motherboard you have, there should be some sort of monitoring softare that came with it, open it up so you can see the voltages, and then fire up wow and see which one falls off. if your psu is a multi rail unit, you can more than likely just load a different rail, or balance it out. but this happening the same time as a driver update is kind of odd. have you tried doing a rollback (using the old drivers) and see if it still happens?other than that driver have you done windows update or anything? does it do it with a solo client as well?