I was using a stock button from the Encore CS4 Library (Corporate: Blue Sky Video Button), which has a very subtle highlight: a thin bar across the bottom of the video frame. I found this highlight too thin and hard to see, so I went into Photoshop, deleted the vector mask, and created another one. I made a vector mask which was big enough to surround the entire video frame, then rasterized it, and "erased" the middle of the mask, to create a "picture frame" for the video window of the button.
This all looks great in Encore. Each picture frame lines up perfectly on its video button. But when I attempt to preview the DVD by right-clicking on the menu window and choosing "Preview from Here," all the frames I've created are just slightly off -- enough to make it obviously a mistake.
Why, if the frames line up perfectly in the Menu window and in Photoshop, do they move when I click "Preview from Here"?