strange shutdown

Old computers power supply caught fire. So build a new machine 4 days ago and it has been running continuously but not completely finished/sealed up(sides and top off) due to my microATX case only having slots for 2 HDDs. So yesterday I purchased an adaptor to fit my 3rd drive into a 5.25 bay sealed everything up and it ran fine for 2 hours then midprocesses it shut off completely. The power button on the front of the case blinked green/orange and would not restart until i flipped the hard switch on the back of the case. It then did the same think while booting up the 2nd time. I let it sit over night and here I am and its been running for a few hours now no problem. Any Ideas?

 

I wonder if it was a glich in your fans then over heated ... gathered this from 'Antec' site..

Temperature-response system ensures blissfully quiet operation, by varying fan speed in response to load and conditions.

http://www.antec.com/us/productDetails.php?ProdID=24480