when i was playing with the programming of the car, i clicked something (never ever click "something", always check to see, what you are clicking!!!), and when I shut off the car, the residual heating fan was on - engine cold, so there was no heat coming, but the fan was on and no HVAC controls would do anything... I started the car, I shut it off, I ran it on Max, on Min, on whatever setting - nothing, the fan kept on going... I left it for about an hour, it kept on going...

So, I disconnected the battery for about an hour, and that "fixed" the issue... Did not have anything like that since than, but the programming did mess up the pano once - I had to go through reset procedure...

Your GM may have gone nuts, try to disconnect battery for some time, it might help... Even though, I think Slick is right...