I created a book trailer using PD10. Now the author wants me to change the cover image which is the first frame of the video. It has a great flip right transition to the next clip. The whole thing is rendered. I was able to remove the book cover frame. When I tried to put the transition between the new cover and the rest of the video, it didn't work. There was only a dark screen between the cover and the start of the video. How do I dix this?