My flat screen will display on the HDMI through start up, until it's time for it to load my user account/profile at which point the screen goes blank. Is this a resolution issue? I'm not sure how to fix it, as I want to dual monitor my computer. My graphics card supports it, and was doing it until I reformatted my computer. It is odd because it works until load up of my user profile.
first off have you tried running in safe mode? and seeing if that works and making sure your video driver is up to date. or make sure you didnt change settings by chance? or try a different cable see if that helps