Also, do you have any connectors installed between the probe and the PID or are the leads from the probe directly wired into the back of the PID with no other hardware between?
EDIT: AH... nevermind. I see that the probe has only 3" leads on it, so I am assuming you extended the leads. Did you use proper thermocouple wire to make the entensions? Thermocouples are sensitive little boogers and should use proper thermocouple wire and connectors or the readings can go wonky.