DVDplayer suddenly fails with mountain lion

The DVD is OK because I can play it using VLC.

What happened was that DVD player still gave the sound - it was playing the DVD - but only displayed a black & white chessboard. I tried lots of things, but it was consistently not working and I had to use VLC. The DVD was a number of episodes and DVD player had worked with the previous ones - but now even those didn't work.

On the console, I find these messages:

"

31/07/2012 19:55:22.944 DVD Player[10319]: It does not make sense to draw an image when [NSGraphicsContext currentContext] is nil. This is a programming error. Break on void _NSWarnForDrawingImageWithNoCurrentContext() to debug. This will be logged only once. This may break in the future.

31/07/2012 19:59:50.398 DVD Player[10342]: It does not make sense to draw an image when [NSGraphicsContext currentContext] is nil. This is a programming error. Break on void _NSWarnForDrawingImageWithNoCurrentContext() to debug. This will be logged only once. This may break in the future.

"

Any ideas??