I've had similar 'ghost video' and 'ghost audio' issues in recent vesrions of MEP, including MEP 2014. They are obscure bugs and I suspect your problem has a similar cause.
Maybe a Music Maker user can help further, but meanwhile I assume you've tried a fresh project and also resetting the program settings to their defaults?
Once when I loaded the project - it hung up on the video file that was in the project but not seen. - This video file was on my desktop - I deleted the video file closed the project and reopened it - when loading the files it came up and the video file - "unable to locate" - I hit skip - and save the project with a new name.
Halloween is over and so are the Ghost video files