HELP! My Pioneer VSX-1020-K receiver is acting up!

[Steelmaker]

There's something wrong with my receiver. I'm getting a faint muffled sound through my speakers when I try to watch something. Yet when I go into the speaker set up menu and run the diagnostic, the speakers sound clear and boomy. Then when I go back to the PS3, the sounds are faint and muffled. I switched it to cable and it's doing the same thing on cable. I suspect that I have mistakenly tripped a setting or something on the receiver but I'm not sure. Any help would be greatly appreciated!