I did the same thing to a system of mine...

...Reset the priority to idle (setting = 64)!!
normal actually uses the cpu consistently, instead of just on idle cycles (which is the best setting for a computer that is used to do other things concurrently). This causes numerous application hangs on a system that you will see in the event log.
Use the other settings only on a cow that does nothing but crunch ECC2 all day, because then you don't need the other power.