Make sure you are using the latest version. It might be a bug that has been fixed.
If it still occurs, contact their technical support.
If they are no help, try simplifying your DVD structure to identify where it's falling down - for example, if each menu screen has audio, try a project with silent menus.
Or try a different authoring package. (I've used the free version of MuxMan and found it to be pretty solid, but it's only really designed to do simple projects. I don't know how the pay "professional" version compares.)