In most cases where the video is cut off, you can typically correct this issue by changing the output resolution settings within the cablebox. I would recommend trying to switch between 1080i and 1080p to see if this corrects the display. Also, in SlingPlayer on Newwatch.Slingbox.Com, there are Zoom and Aspect Ratio controls located directly beneath the video window that you can further adjust to your liking.
Hope this helps!
Sling Media Forum Moderation Team