My Itunes won't play the video, only the videos audio?? black screen??

This is my second post with my problems with Itunes today, but it's ANOTHERRRRRRRRRRR stupid problem. (Starting to hate apple now, like I said, they are getting difficult and hard to use)
When I go to play a video on my itunes library on my mac, it just shows a blank screen and then the audio still plays. This happens to all my videos.... how do i fix this??

Thanks!