I had this happen quite a few times on mine. I finally took the boot off all the way, wiped it down with brake cleaner and coated it with a tack spray, stuck it back on and no more problems.
This happened to me towing our 5er up a long steep grade pushing the truck way to hard trying to get home. BD makes and upgrade boot and clamp kit for the trucks that will help eliminate boot blow off. I fixed the blown off boot in a NAPA's parking lot with my wife's Strydex acne pads to clean the boot and mating surfaces and then I used her hairspray when I put it back together. By the way when the clamp lets go at 32lbs of boost it makes one hell of bang.....