That's a very strange PSU to end up in a home PC. It's designed for servers, and older ones at that. It may be decent, I can't say, but it's certainly not right for your PC at all. Your newer PC needs mostly 12V power. Easily 10 amps, likely more under stress.
It probably got a little warm, less efficient, and that was enough to trip the protection on it.
However, 50c at idle is a very poor CPU temp.
Different programs use different baselines to measure temps. So let's be sure we are on the same page.
What does this program:http://www.cpuid.com/softwares/hwmonitor.html
Report as the minimum and maximum temps for all 4 of your cores? Go ahead and work the CPU a little bit (with HWMonitor running) so we can see what max temps are.