Every time I edit something in Vegas, the preview screen does something weird. Whenever I adjust the screen size, the screen stretch's without filling the aspect ratio; whenever I edit a track, the edits don't show up; and if I move the tool on the timeline, the screen stays stagnant. I don't know what's going on with the program or why this is happening, and I definitely don't know how I'm meant to change it, this has never happened to me before.