if this shutdown issue began with the processor upgrade... i suspect overheating.
did you put a SMALL dab of thermal paste on the new cpu before putting the Cooling heatsink and fan onto it?
is the cooling fan turning fr the cpu?
the shutdown is a safety feature so you don't burn up the cpu. THEY RUN HOTTTT !
if you put more than a SMALL dab of heat sink paste and it has gone all over remove the heatsink-fan combo and careffully remove the cpu.
you need to CAREFULLY clean both of these with isoprophyl alcohol and a q-tip or some similar device.
DO NOT SCAPE using anything hard with any real amount of force, your goal is to clean not scour.
visually check to see if any thermal paste oozed into the pins of the cpu or anywhere else outside of the cpu
let this dry for 30 minutes (i know that's overkill-but you need to be calm, carefull and patient when doing this) when you are relaxed and it is dry..
do the SMALL dab of paste (some say the size of a BB) in the center of the cpu, remount carefully the heatsink-fan combo, plug the fan in and with luck...
you should be up and running.