Nope, not much advice to give.
You're somehow mising the footage: you'll notice that its place in the project window shows color bars. Double-click on it, navigate to the location of the missing footage, double-click again and it should be there. Save the project before you render.
If it's some other issue, try answering the questions you'll find here so we can do a proper diagnosis.
North America
Europe, Middle East and Africa
Asia Pacific