I am using Sony Vegas 6.0 and am creating a football highlights DVD with music and text. My problem is that when I open the project, someof my video clips appear as black boxes in the timeline and in the preview pane. I do not get a "media offline" message and the video clips that are black seem to change every time I open the project; sometimes in the beginning of the timeline, and other times towards the end. I am not very proficient in video editing, but am a quick study and have basically learned from just trying out, but perhaps I did something I should not have. Any ideas?