I have had warranty work on mine 4 times. I am almost to the point of claiming a lemon on it. I have had it since new and we had issues starting about 35k miles. I have had the coolant system flushed umpteen times, the radiator and heater cores replaced maybe a total of 7 times (sometimes it was changed multiple times per service), and the freon charged as many times.
It is just an issue with the flux in the coolant lines causing a chemical reaction with the coolant that gums everything up. And when that happens... the heater core is used to keep the A/C from freezing up. When the A/C runs it will build up condensation and freeze it... and that causes all sorts of issues. (I actually had similar happening on my home HVAC around the first time we had this with the car).
There is a bulletin and it should be covered under warranty.