I'm slowly tweaking my my new build to my liking.
This is a quasi-HTPC build hooked up to my 46" Panasonic Plasma screen.
When I switch inputs on the TV and later return to the one the computer is on, I get a popup saying that my audio has been disabled and that the "device" (I'm not sure if that means the TV or the GPU) doesn't support HD Audio.
This also occurs when turning the TV back on.
To correct the issue, I simply log out of Windows and log right back in.
My question is, How the heck can I prevent this from happening in the first place?
I've set the TV as the default device for audio and display in Windows and, insofar as I can tell, Catalyst.
It's simple: you got your sound played by HDMI channel.
Most modern sound and video cards have separate HDMI sound channel, which works only if you connect sound to sound devices through HDMI cables.
For example, there are sound systems and headphones that have such types of connections.
These are not common, so usually when you turn that function ON ("sound through HDMI"), without any sound device that has that type of connection on the receiving end, you won't get any sound.
So, basically, your TV/Monitor/Screen doesn't support that, thus it doesn't have sound, and tells you so.
It also usually happens to integrated sound chips on motherboards, because Windows tends to use that option automatically by default when a new device (be that TV screen, or headphones, or even just speakers) that has sound output is connected.
The best way to fix that is to use discrete sound card (like Asus' Xonar, Creative's X-Fi, Yamaha's D1S, VIA's cards, and etc., and etc).
So, basically, just try using a discrete sound card, not integrated sound chip in your motherboard. And make sure that sound settings are not at HDMI input/output.
I hope it will help you somewhat, even though I won't be saying that this is 100% your case. Just try it, if it helps, then I was right.