HDMI Audio not showing in playback devices???

I have an HTPC that I use to watch TV through Media Center with an HD Homerun Prime. Lately I've been getting an error message in Media Center that say something to the effect of "no audio device detected." When I close out of Media Center, I notice that the little speaker icon in the bottom right of the screen shows that the volume is muted. If I right-click on the speaker icon, and select "Playback Devices," the HDMI Audio is not listed. It's usually listed as something like "Denon Receiver - Digital Audio".

Anyway, I've right-clicked in the Playback Devices dialog and made sure that I have both "display disconnected devices" and "display disabled devices" checked. Even with those settings, it's still not showing the HDMI Audio. It's as if the cable was completely removed, even though the video is getting through.

Does anyone have any ideas of what could be causing this issue? This HTPC has been working without this issue for years now, so I'm not sure why this issue is suddenly popping up, but it's really annoying. I haven't installed any new software or made any hardware changes that I can recall.

Here are my specs:

HTPC: Intel Celeron with onboard graphics (HD4000, I think);
Receiver: Denon with HDMI inputs;
TV: LG 50" plasma.

I should mention that I have the HDMI cable running from the computer to the receiver, and then an output from the receiver to the TV.

Thanks,

Kevin

Thanks for the response. I'll check the device manager when I get home. I had checked for any error codes, and didn't see any, but I don't remember which specific devices were listed.

BTW, the problem is intermittent. I've "fixed it" several times, but I'm not sure what I've done to fix it. Generally, I restart the computer, turn off the TV and receiver, turn everything back on, etc. Eventually it shows up and I can enable it in the playback devices window.

Kevin

Ok... I checked and there are two items under Sound in the Device Manager... the first is Via High Def. Audio, and the second is the Intel Display Audio. I disabled the Via audio and restarted. That didn't work. I checked the Intel driver and its up to date. I uninstalled the Intel driver from device manager and scanned for hardware changes. It recognized the Intel audio and reinstalled the driver... still not showing in Playback Devices... can someone help? This is really annoying!

I tried switching out the HDMI cable from the HTPC to the AVR, but that didn't help. The cable from the AVR to the TV is like 15' long and goes through the wall behind the TV. Replacing it means I'd have to take the TV off the wall, etc... kind of a PIA.

Anyway, I don't think that's the problem. I think the problem is my Denon AVR 1513. For some reason, when the AVR is off, the HDMI passes through from the HTPC to the TV (via the AVR that's off), and the Denon AVR shows under Playback Devices. If I turn the TV speaker up, the sound comes through fine. This works only sometimes though. Other times, when I turn off the AVR, the Denon HDMI audio still doesn't show in Playback devices.

On my AVR, I set the HDMI Audio Out to "TV" from "Amp." Now, when the AVR is on, the sound passes through to the TV speakers, and the Denon HDMI Audio shows in Playback devices... this makes no sense to me. Maybe my AVR is shot???