Created attachment 101200 [details]
Screenshot of menubar shaped artifact during presentation
When I try to present a document in slide show mode, when using two screens, there is some shading at the top of the slide that looks as if it is about the same size as a menu bar (see image). If I position my mouse in the window with the slide-show the artifact goes away, but if I have the mouse on the presenter window, the artifact is visible.
That is a known Compiz/Unity issue.