Rambo: First Blood Sound quality

[Pirendeus]

I just watched First Blood for the first time tonight, and the non-center speaker sound was practically mute. The blu-ray.com review gave the sound a high rating (including bass and surround), but even when I maxed the volume, I had to stand a couple feet from the rest of my speakers to hear anything. Even the explosions seemed to emanate almost entirely from the center speaker, with the subwoofer output very minimal.
I tried using both available audio outputs (DD 5.1 and DTS HD 5.1), but nothing changed. I've never had this problem with any other movie. My receiver (onkyo HT-S9100THX) should be able to handle any audio with ease, especially a blu-ray thats been out for years, and I just can't figure out what is wrong.
Thoughts?