I have a thin, bright white frame around the outside edge of my 16x9 screen, when playing movies with WinDVD. I'm using a DILA, at a resolution of 1360x768. The frame is always around the edge of the display area, regardless of the aspect ratio of the movie.
This may or may not be related, but I found that if you have WinDVD set to open in full screen and then specify maximised in the command that launches it you get this problem. For instance I use Girder to launch WinDVD and girder was set for maximize. Igto the white border. When I set Girder to launch WinDVD in 'normal' the whit border went away.
you might want to check that whichever way you launch WinDVD you say 'normal'