I've had informal conversations with the program's writer, and also have done research on the problem. Apparently the shutdowns are triggered by illegal memory access by the program; the system shuts down as protection.
If I'm not mistaken, some viruses can do this as well. Can anyone confirm?
Anyone looking for something else I have been using a program called 'coretemeter' which seems just as accurate as coretemp and doesnt seem to crash the PC (it has restarted once during stress testing, but that was when I was trying out a lower vcore - so that was probably the cause of the crash)