Yeah those temperatures are definitely a bit high. Ideally you want 30-35 on idle and 60-65 on full load... or better
I would remove the heatsink and give it a good clean then re-apply some quality thermal paste such as Arctic Cooling MX-4.
Unless this over-clocked? In which case you may need to look at reducing voltages, clockspeed or getting better cooling.
Have a quick read of this to make sure you have the case fans set up correctly too - http://www.tomshardware.com/reviews/cooling-air-pressure-heatsink,3058-5.html