cpu voltage too high, faulty temp sensor, warning threshhold too low, poorly installed heatsink, fan not up to speed, poor heatsink or cpu surface. bad chip/die contact. bad retention bracket or springs. other heat sourses in the computer. poor airflow.
^+1. pushpins arent seated correctly. also check for case ventilation... no case fans wont cause ridiculously high temps, but case fans do have a surprising effect on temps... other than that, get a new cooler. my e5200 cooler is still sitting in its plastic box. useless, tiny, aluminium POS.