It does happen................I guess I have seen every PC component trashed through overclocking.

What happens is that people sort of get it right, but they set their shutdown threshold temperature too high. They also fail to add suitable additional ventilation and keep their fans clean.

Over a period of time, crud gathers in the heatsinks and fans, temperatures build up, and components fail. This is quite insidious as opposed to the traumatic overclocking failures you describe.

In this case though, I think that the UPS is the prime suspect.