Cant preview video in subtitle workshop ?

When i open a subtitle to work with the movie start automaticly and the sub is there. But the video preview mode is totaly black !? I have sound and everything but no image ? What im a missing ?

// Thanks..

 

Have you verified that the video codec for that particular file is installed?

 

I thought i tried them all, every code-pack i could find i tried, but the solution was that i have window vista and there is a special code-pack for that. So now it works =) Thanks