I'm getting a significant popping noise when I skip chapters on a dvd.

Up until 2 days ago I was running a 950, an ICBM and 4 Adcom amps for a 5.1 set-up. With this, I had no popping noises at all.

Just a couple of days ago I moved up to a 7.1 set-up. I added an additional Adcom amp, a second set of rear surrounds and had to remove the ICBM from the line-up as it's only good up to 6.1.

Now, I get this annoying "popping" sound whenever I skip chapters or when the dvd plays through movie previews or when I skip through material I don't want to see.

Anyway to fix this without going back to my old set-up and 5.1?