Replacing the processor is straightforward. Details in the manual:
http://www.asrock.com/Drivers/Manual/P4VT8P_UM.pdf
For a fairly new computer this all seems mysterious tho. I would run with the case open & verify that the fans are running well. Also see if you notice any extreem heat off of the CPU. Try a defrag & see if you notice a major heat shift.
& don't forget the warranty!
Any new dumps?