Hmmm ... maybe I had a similar problem recently when I played Transformers 2. In the scene where you would expect the most bass the bass disappeared! My first thought was it has to do with the mix which has the bass in the .1 channel for this scene. My sub is not really up to par with the rest of the system and I have the feeling the calibration with MRC went not well with the sub. Reading this thread I am not that sure it has to do with the mix and .1 channel ...