Due to a change in the way Motion renders some title generators (Final Cut Pro has Motion’s rendering software built in), changing their opacity will effect all the footage below the text.
Instead of using fade in and fade out controls in titles, some people like to use adjust the opacity parameter using the Video Animation curve editor. However, if you use a graph like this…
…in the frame before the title generator, the main storyline is fully visible. On the first frame that is overlayed by the title, the 0% opacity value is applied to the storyline as well – producing a black screen. As the opacity rises to 100%, the video and the title fade back up.
If a title you like to use produces this effect, instead of modifying the opacity graph, apply the Cross Dissolve transition to the title (Select it and press Command-T):
Check out my other free effects and articles on my Final Cut Pro X home page.