Posted this issue last night under the PSU forum, hoping to get a little additional insight:
Having some trouble with a new build: built my new system and had it up and running just fine, but after 45 mins the system abruptly shut off. I wasn't doing anything too intensive (downloading new drivers in the background while surfing the internet) and charging my phone in one of the front USB 3.0 ports. Pressing the power button would allow the power button LED to blink on then immediately off.
I opened the case and unplugged the power from the video card, and now everything appears to work fine. Monitor was plugged into the graphics card, rather than the MOBO DVI spot.
I've checked the HSF, and it is installed correctly; temps are running 28 C and 23 C for CPU and MOBO respectively. I'm trying to determine where to go next: is it possible I'm looking at a bad GFX card (maybe there's a short inside) or PSU?
CPU: Intel i5 3570k
MOBO: Asus P8Z77-V LE Plus
GPU: EVGA GeForce GTX550 Ti
RAM: G.Skill Ripjaws (2x4GB)
SSD: Crucial M4 128 GB
PSU: Rosewill Hive 550w
Case: Cooler Master HAF XM