Bad RAM and system corruption
This post reminded me that I also ran into a system with strange corruption recently, but it had nothing to do with overclocking. In my case, it was bad RAM.
It took me a while to clue in. My system would randomly crash, documents I was working with would get corrupted in RAM (I'd scroll the document and I could see bad portions of it, changing as I'd scroll it into and out of view).
I used the Microsoft Memory Diagnostic to verify that it was bad RAM. After swapping the RAM, no more problems.
Maybe overclocking can cause memory errors?