Rear speakers not receiving signal

[kevinokev]

Long story short: My friend's rear speakers aren't receiving signal.
I did re-run the rear speaker wires to the center to confirm the speakers and the wires work and they do. There is some setting in the receiver that is impeding the signal. The receiver is a Sony STR-DH520 and the display is showing that 5 channels are being output. The DVD player is an Xbox 360 connected via HDMI to the reciever and the Xbox is set up to output multi-channel audio. I set the equipment up prior and everything worked as intended for a few months. Not sure if my friends kid hit a button or something. Is there a way to do a system reset or do you know of another means of troubleshooting? Thanks for any help you could lend.