TX-NR509 multi-channel PCM

I'm playing 5.1 channel, 24 bit, 96kHz PCM wav files on my WDTV live, which is connected to my NR509 receiver via HDMI. When I view the receiver input info it says MCH PCM, 5.1, 96kHz, etc. Similarly, the output info also says 5.1. However, sound is output through the left and right speakers only (nothing from the centre or surround speakers). Instead it sounds like the centre and surround channels are output through the left and right speakers as well.
This has me confused because the receiver plays multichannel PCM, DTS-MA and TrueHD from a blu-ray with no problems. Any help with this would be appreciated. Thanks!

Hi jamesb,
I have a co-worker looking into this and will get back to you with their answer soon, thank you.

Hi jamesb,
You need to configure your western Digital TV to output a 5.1.. Because the receiver is seeing the signal as just 2 channels coming in. The receiver is somehow down sampling the signal in which we have no control over. Thank you for contacting Product Support via our forum.