Hi,

> If I open a DVD film file with MPlayer from the DVD disk (for example
> VIDEO_TS.VOB) i get the following fatal error message displayed by MPlayer:
>
> Fatal Error! Error opening/initializing the selected video_out (vo) device

Go to MPlayer settings and try a different video_out device. Just go to
Preferences -> Video and choose a different driver; that's the way I got it
working. If you have a good opengl graphics card, try out the "gl" driver.

hope it helped.