OS - Windows 7
CPU - I7
not much else - the pc would output sound to the TV via HDMI
if I turn off the TV overnight, the PC doesn't output sound via HDMI - and I have to reboot the PC to get sound back.
this is very producible - I'm surprise you didn't turn off the TV/HDMI in your regression test
Also, the PC/OS Windows 7 default the sound output via HDMI - since the TV has sound output
you can see the default audio device in the control panel - set to HDMI when PC first boot.
When you turn off the TV - and comes back the next morning turning on the TV, the audio
device via HDMI disapear from the default audio in the control panel, it doesn't restore the audio HDMI
when the TV is turn on again .