I'm going to take a guess here: you're using Motherboard Monitor (MBM) to monitor you system, correct? I'll bet that you have the wrong label on the wrong sensor.
IOW, the MBM little box says "CPU Temp" but it's connected to the MOTHERBOARD thermistor instead of the CPU thermistor. Conversely, the Case Temp sensor is connected to the CPU thermistor.
Just go into MBM and switch sensors and all will be well. I do this all the time...it's nerve-wracking. Good luck.