On my newly built HTPC I'm using HDMI out to my HDTV. I'm running Windows 7 64bit. When I turn my TV off in the evening, then back on again in the morning, I have no video signal. Sometimes it returns when I VNC to the HTPC and change the resolution, but that isn't exactly a fix. Any ideas? Is there some limitation of HDMI that I'm unaware of that causes this to happen?
HDMI devices do something called a "handshake" to detect each other when turned on or connected. In many cases the order in which they are turned on affects this.
Try altering the order that you turn them on. I don't know how long it takes for this to happen when you boot the HTPC so try it already on first.