Video location error (case 11665)

[kitresearcher]

I'm using Medialab 2012 on a new Windows computer. I'm presenting a series of movie files, but when I run the file, some of the videos randomly appear in the top-left corner of the screen with a black square in the middle where the videos should be located. All the videos run fine if opened directly through Windows Media Player or Quicktime. Which videos get shifted over changes mostly randomly every time the file is run. Has anyone had this problem and discovered a solution? I've read the other threads about other ways of presenting videos, but they all seem to give the user video playback controls and we can't have our participants pausing or rewinding the videos.