With the Fuse card, if I hold down the mouse button for a long time or do another lengthy operation, the video preview disappears. Why?
The Fuse card requires a periodic refresh to keep the video preview present. If the card is not refreshed in time–because you are doing something that is keeping the computer busy–the video output will revert to its idle display, which may be black, blue, or color bars. Releasing the mouse button will redisplay the correct video preview.