The sensors aren't meant to be 100% accurate. They're meant to provide data for the CPU fan controller to keep the fan going as slowly as necessary to keep the CPU only as cool as it needs to be, at stock. Worrying about a couple of degrees difference for one core is usually not worth it.
Thanks everyone else for the help.
Edited by Lambent Darkness 7 - 12/21/08 at 7:00pm