Whoa, that's weird.
Have you checked your clipping planes? In the panel there, go to Camera > Select Camera. Press CTRL+A to bring up the attribute editor. In the window that will either pop up or appear where the channel box is, find the Near Clip Plane and Far Clip Plane. I usually set the NCP to .001 and the FCP to 10000.
Your issue might not be that as the CP won't cut off only half the screen like that, but it's a start. My next guess would be there's something to do with your vid card. Have you updated drivers recently? What card are you using?
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida