Have them check if your coolant heater failed.I know that the subject was entertained before. ..
No, i rarely run the defroster. A few rare occasions when I'm parked, ready to go to work @4am and the windshield is icey. That's all .My windshield fogged up rather suddenly for the first time the other day too. But as soon as I turned on the defroster it cleared right up. (I generally keep that toggled off; I think this is the first time I turned it on in the two months that I’ve owned the car)
Did the problems that you to above had occur while the defroster was running?