Video preview disappears after adding a color balance node I was trying to color grade a video in the "composite" mode, then I selected "use nodes". I could see 2 nodes in the compositor. No probs.
 But when I tryed to add between these nodes a color balance node, my video preview disappeared as you can see in pictures I sent.

Somebody could Help me?
Your video needs to be added to the composite in the form of a Movie Clip node or as frames in an image sequence node, and then add a Viewer node as output to see the feedback in the backdrop.
Right now, you have a renderlayer node from your scene which probably only gets you the default cube.