I also have this issue. I am using Win 8.1 with a Asrock Z87 MB, i5-4670 on the PC. I then am connected via HDMI to a Pioneer SC-1222k receiver. The Pioneer receiver is then connected to an Epson 5030 projector. If I turn off the receiver, when I turn it back on, no HDMI audio is detected on the PC. It requires a reboot.
Its interesting to note that with the Intel HDMI audio drivers, it shows my receiver as the audio device (SC-1222k) in the audio device control panel in my PC, not as Intel HDMI Audio. It appears to not detect this device when it is repowered. I've tried it with HDMI CEC both on and off in the receiver.
This is approximately my 10th HTPC build in the past 7 years and I've always used them with various receivers and projectors/monitors. This is the first time I've had an issue like this.
Any insight from anyone is appreciated. Is my only option to go back to Windows 7 or a discrete video card? I actually prefer Win 7, but I do like the video and sound quality of the Netflix Metro app. Considering Live TV and Blu ray are my primary considerations, I better start my Win 7 build.