I was poking around the inside of my computer, I just built it a week ago. I was seeing if I could position a fan header wire better for a cleaner looking inside. When I was done and I booted it it posted successfully and after the motherboard splash screen the display banded in weird colours and froze. I rebooted to the same result and when I shifted my hdmi cable to the motherboard the screen went to sleep and was completely unresponsive.
I first checked the sata power and data cables on my hdd. They seemed ok but they may have been a bit loose. I'm not sure. I pushed them in and I think the power cable went in a little more. My computer booted successfully after that and I shut down and restarted several times and everything was fine.
The thing is I don't know what caused this. Could a loose power or data cable on the hdd have been responsible? Why was the motherboard hdmi not responding in the same way and turning the screen off? (even that is fine now)