Very sorry to hear about your speaker. Sad

Does it always happen in the same place in the movie (like if you rewind, will it happen again)?

Since plugging in the optical cable, have you unplugged the analog cables? Any DTS-capable receiver will note in the manual that DTS soundtracks cause players to output noise from the analog outputs; some receivers have precautions to avoid the analog inputs from being used at all when the DTS decoder is in use. I couldn't tell you why this happens at all, but I never connect analog audio cables to an input on my receiver if I intend on using digital audio with that input.

I would suggest also reposting this in the Home Audio & Video forum. You'll get a different audience, and there are definitely folks over there who are quite knowledgeable with regard to this type of thing. Have you called Denon yet?