I was driving to work today, and suddenly the vent started blowing hot air. Not warm, hot. The rheostat was turned all the way to the cool side (eg, the heat was not on). Pushing the AC button didn't help. Turning off the fan didn't really help, hot air was till coming up, with a bit of an almost burning smell. I checked the PEM/Engine/Battery heat indicator and all were firmly in the blue and not budging towards the right. I could not get this to stop. About 5 miles later, I started getting warnings from the system that there was a coolant system problem and service was required. It gave me this message 3 times in quick succession (I kept clearing the screen to watch the temps). Of course, when I finally parked at work, I could not get those errors to come up to record the actual code... Looking under the hood, nothing seemed ununsual. There was coolant running in the system in the trunk by the battery as there should be. Any ideas?