Happy holidays everyone!

Santa was good to me this year, bringing a Samsung BD-P1500 Bluray player. I also received three movies and Firefly (!). So far, though, I've run into one problem:

On The Dark Knight, I get this problem where the sound keeps cutting out. It ranges from .25-1 second, so not long, but it happens enough to be highly distracting. Oddly, it appears to happen during loud scenes, particularly when there's a big rumbling. So not just explosions, but when something is knocked down by that explosion. Or when the Tumbler plows through a wall - stuff like that. When it happens, all the speaker indicators go out on the receiver like there's no audio input. It's very strange, because I've watched good long portions of a couple other movies on it (Wall-E and Sunshine - an excellent space thriller) and neither had this problem, though neither had these kinds of explosions, but Sunshine has some very loud scenes.

As far as setup goes, I've got optical audio from the Samsung to my Sony (STR-DE985, I believe) receiver, and HDMI from the Samsung to my TV (clearly, I'm not using the audio from the HDMI cable). The Samsung is outputting bitstream, since I couldn't get surround out of my receiver any other way, and the DVD player it replaced was also doing bitstream.

So does anyone have any suggestions for what might be happening?