Yes, I realize that you said you had deleted all projects and events but one. What I need to know is the steps that you took to delete the projects and events, and to establish that they in fact were correctly deleted.
Go to your Movies folder (Go/Home/Movies) and control click on your library's icon. Then click on Show Package Contents in the drop down menu. A folder will pop up showing all of the projects and events that are in the library. Take a screen shot of the folder and post it along with a description of what you see in there. Don't move or change anything.
If you had correctly deleted from the library all of the projects and events but one then there should be nothing in the Show Package Contents but that one undeleted project and about 4 temp and plist files. If more projects are shown in the Show Package Contents then they were not actually deleted. In that's the case, would you describe the steps that you had taken to delete the projects and events so that we can track down what went wrong.
-- Rich