1. If the source video is a component video input, then you will not see anything but a black screen with the menu overlaid until you exit the menu. The 990 overlays the menu onto the source video for composite and s-video sources, but it replaces the signal from component video sources with a blank screen.

2. Do any other sources display over the component video monitor output? That'd help troubleshoot the issue (determine if the video switching is working and if your display accepts 480i component video).