^^me too^^
any way you can switch it out with say, a friends cpu? see if it has the same problem?
it sounds like a processor problem to me as well...
you say you were having this same problem for one year before your old mobo died?
i would suggest, if you cant lay your hands on another p4 from a buddy to test with, that you go ahead and change (ie buy a new one) the cpu. seems like you have pretty much tried everything else.