This isn't a 100% certain diagnosis by any means, but the following was taken from the review of your PSU.
"Normally, this unit would have only gotten a half point deduction there because of the near excellent numbers I got in the hot box. But... this unit shut down in the hot box, dropping all outputs to zero."
Here's the full review
It seems that model does not tolerate heat well at all. Perhaps you can try removing the side cover of your case to see if that stops it...