DVD Lab Pro Menu, it's skipping items?

My DVD Lab Pro project menu seems to be skipping items. For example, I have 4 separate video files and 4 menu items pointing to these video files. I can select all 4 one at a time using the mouse on the computer, but after it's burned to a DVD it skips from 1 to 3 and I don't seem to be able to select 2 or 4. Anyone know why and how to fix it? Thanks!