Cpu heat is Ok. Im using a silver arrow extreme , and there hasnt been a problem with temps yet. Its at 45 degrees when it has cut off.
when it all cut off please press on your GPU into the socket maybe it isnt well fitted
(happened to me with my first rig so i just putted a piece of plastic to secure it
and may i ask , is the gtx 480 from a different manufacturer than nvidia like xfx or asus or such)