Universal DVD audio problems

[BigDaddyX2]

Hi, I'm a long-time-listener-first-time-caller. I tried doing a forum search on anything pertaining to this subject and I couldn't find one. So here goes.

I've had problems with Universal DVD's since I could remember, but not with all releases. I usually experience a noticeable dip in sound volume when things are supposed to get pretty loud (i.e.: an explosion, gunfight, airplane/helicopter fly-bye, car crash, etc.) and it usually continues for 15-20 seconds afterwards. It gets really annoying because you can't hear what people are trying to say at the time and I have to crank the volume up, then turn it back down when things "normalize". I have the same results when playing the movies on my old-ass DVD player and my 60gb PS3.

Here's my system's specs:
Receiver - Sony STR-DE985(Black model)
DVD Player - Sony DVP-S530D

I do use the TOSLINK audio hook-up for both the DVD player and PS3. The receiver doesn't have an HDMI connection and I plan on upgrading it soon.

Here's a list of some of the movies that I've noticed audio changes in:
Shaun of the Dead
Hot Fuzz
Hulk (2003)
The Mummy + sequels
Dawn of the Dead (2004)
U-571
And the list goes on and on...

But here are some that have no changes:
Gladiator
Back to the Future Trilogy
I'm sure there's more but it's late and I can't think that clearly.

I don't have any sound issues with any other sound studio; just Universal. And that worries me because they are going to start releasing movies on BD soon. I was wondering if anyone else has had this problem, and if so, how did you fix it (if at all)? If you haven't had any problems with Universal DVD's, do you have any insight in this matter? Thanks in advance.