Could be a faulty PSU, i.e. the minimum power draw circuit within the PSU. I would open a thread on the corsair forum to ask the Corsair gurus there to investigate.
http://forum.corsair.com/v3/forumdisplay.php?f=178
EDIT: I see you already did that, bu...
http://forum.corsair.com/v3/forumdisplay.php?f=178
EDIT: I see you already did that, bu...