you need to take out the CPU in order to check whats really happen to the problem..
just make sure, nobody is disturbing you..
in a quiet room...
and slowly take out the fan.. and slowly take out the CPU.. and
the moment you take out the CPU. it will be very obvious to see whether is there any bended pins on the Processor socket..
if there is.. please get the black plastic processor cover to protect the processor contacts..
and send the board for repair