When I use Konqueror the little "movie box" starts to play with the Kaffeine (Xine) plug in but If I use Firefox the main Kaffeine program opens and I watch it that way instaed of little "movie box". I can watch it full screen.
This reminds me of the old joke about the man who goes to his doctor and says"It hurts when I do this,Doc. What should I do?" The Doctor replies"Stop doing it then!"
It depends on which browser and which movie plugin you are using. If it's Internet Explorer, I would suggest updating whatever movie player it is; windows media, quicktime, realplayer, etc.