The Video subsystem can be manually enabled or disabled, by selecting Options -> Video/CD+G -> Video System Enabled
Alternatively, the Video subsystem can be toggled on or off by pressing Ctrl+Alt+Shift+V on your keyboard.
Tip: The Options -> Video/CD+G menu options can also be accessed by right-clicking your mouse on the middle video display, when they are visible. This is the suggested method, as it is the quickest way to access the Video/CD+G features.