Lo m8, I had the very same prob ie as soon as I plugged the mach II in the temp would rise to over 80C (with out the actual unit being tunred on) it would then give that error.

But my unit had worked fine up till that point, anyway I unplugged the unit and left it over night and it was fine in the morning and has been ever since...well for at least a month now.

I think its more of a controller board bug than a dodgy temp sensor myself so hopefully yours will be fine to.