How do I fix a black screen?

I edited a video and it took me a week, I opened the .mlt file and finished the video, when I went back to look at it half of the video screen was black. I have two video sections and one audio sections, they do not overlap each other. If someone could tell me how to get the video to go back to the way it was before, that would help alot. I deleted most of the clips Ive already edited.

You have to provide more information for you to get help and if it is a bug to get it fixed for the next release.

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