I usually try to figure things out by myself, but I can't for the life of me figure out what's wrong with my set up other than potentially an HDMI driver issue..
Let me start off by stating my specs:
Using a Denon AVR-1912 which connects to my PC via HDMI into my Nvidia GTX 670FTW.
On the other end, that plugs into the "BD" HDMI slot.
I have another HDMI cable connecting from the "Monitor ARC" HDMI slot on the Denon AVR to my Dell u2410 Monitor.
I then have the Denon AVR-1912 hooked up to Infinity Primus P153 speakers on the front end channels left and right. As far as I can tell the wire is good and even cut some new cable and made sure left and right matched up appropriately.
For over a year I've had it this way and it hasn't been much of a problem. It would play sound and display my monitor..this is how I get music to play from my PC to my speakers and use my monitor as a display.
I have 2 monitors, if that makes any difference (probabaly not). The other is hooked up to the GTX 670FTW through a DisplayPort connection.
I also have an HSU VTF-3 subwoofer connected via LFE to my Sub-out slot on the Denon AVR.
I'm using Windows 8.1 with the 326.19 driver and suite.
I have no other speakers connected to my AVR and am just looking for simple 2.1 magic.
I've used Audyssey to set up the speakers, to no avail.
Let me be clear: Using Pandora to play music, the subwoofer and speakers have no problem. They output music well and everything is good and right in this world. When I switch to BD/PC mode, sound doesn't work. I've enabled the Denon AVR as the device to use in Windows. So that's not it either..
I think I've given you all the information you'd need to try to diagnose this problem. If you need anything else or pictures let me know.