I had the exact same experience. I have a properly calibrated SVS PB12. When the movie rolled and the helicopter transformed and sent the shockwave out, I paused the movie and got up and checked to make sure the sub didn't get unplugged or something. Other parts of the movie sounded good. But when I watch most well mixed movies, my sub literally sucks the air out of the room.
I thought the surround mix was great, but thought the mix was really lacking on deep, low bass.
Reading the rest of this thread now I wonder what is wrong? My sub should go down to 16hz at high volume. I know in some parts of the movie it sounded ok, but usually I really notice. I really doubt it would be something like faulty disks would it? That doesn't make sense to me.