I am attempting to burn a menu based DVD. I added my project to the timeline, (including chapter markers) then I click on "Theme" to choose the menu background. This adds the menu (and, interestingly, maintains all of my chapter markers in the tree in the upper left workspace), but, the video and audio are now gone from the timeline and only the menu background appears there. I'm pretty much a noob here and it's probably something dumb but I have been trying to figure this out for a week. Any advice is appreciated.

FWIW I found the online tutorials and help for Vegas to be excellent but not so much for DVD Architect. I'm really lost if I try to do anything but burn a single movie. I am using 4.5 Pro (build 69) if that matters. Thanks!