Black Screen after Exporting

Hello, I need help with the following:

I have been working very hard on a project for a long time. I finally try to export today, just like I have on many previous projects, but it exported as a black screen. The audio was still there, but the videos were completely black. I was having other issues yesterday and this morning with it being very slow, so I am assuming there is some sort of software bug? Somebody please help because I am on a deadline with this project and cannot figure out how to solve this issue while exporting.