Larry,
I have Dish not Directv but I've had a similar problem in the past, come to find out it was the receiver. I've blown 2 Dish receivers in the past year and they have always been connected to a good quality surge protector. I believe my problem has something to do with power switching but haven't pin-pointed the problem for sure. In the interim I unplug my Dish receiver surge protector before I do anything (start engine, generator, etc.) that may cause a power surge. Since I've been doing this I've had no failures.