I’ve gone the route of having my Harmony remote shut down WMC (Alt+F4) when I put the system to sleep. It also re-launches WMC (GreenButton) when you turn the system on. This way the handshake is always done with the Windows desktop, not WMC. This has solved all my HDMI issues, which were 1) dropping back to 1024×768 resolution, and 2) black screen.
By the way, you can usually get your screen back from the black-screen by pressing Ctrl+Alt+Del then hitting Esc. The 1024×768 problem requires running back through WMC TV setup.
