Yeah, it's possible that it
could be overheating and tripping the built-in OTP (Over Temperature Protection).
You could buy another el cheapo (or otherwise) PSU locally to try and see how it rolls..It never hurts to have another unit in standby that will work in a pinch.
DON'T use any modular cables from another PSU unless you're
sure they are compatible because PSU/Component damage
could occur.
See the
PSU Shipping Guidelines so that you know how to send it and what/what not to send when RMA'ing.
Use the
OuterVision Power Supply Calculator to estimate your system wattage need and to see some recommended units, a 550-watt unit
may not be enough and
could be causing the problem, it
may be running at or near full capacity..You can also use the
EVGA Power Meter and you'll get a 10%-off discount code (with conditions) in your email, just for using it..The OuterVision Calculator is much more detailed though.