Are you using onboard audio or video on the Asus M4A785-M mobo listed in your signature? If so I suspect that may be the problem. Some of the early mobos with integrated HDMI ports didn't pass audio over HDMI very well, some discrete video cards had trouble passing audio over the HDMI port as well depending on the audio processor, it might be a problem with some settings, or it might be a problem with some drivers, or it may be a problem with the hardware, or a combination of all the above.