If you have that specific moment you want to pause at the video, take a screenshot of that and add your text-box in some image manipulation software to that screenshot.
At this point you can render another video clip in Kino, which would contain your video from to beginning up to this point. Render also another video, which would be from this pause point to the end.
Then you can import the first part of your video to Kino, add that screenshot to storyboard & make it last as long as you like, and then add the last part to storyboard.
However, this approach does not take into account the soundtrack. Should it be quiet while paused? If so, then the method I told you should work. If you need some sound at that point, you probably need a more comprehensive, yet possibly buggy and harder to use solution, such as Cinelerra.