Using Mac OS 10.8.5 Same problem on both 15" MBP and 13" Mac Air. Switching between Design and Code and 1/2 the screen on the top will disappear! Can someone tell me when this will be fixed?

I am sure this is a silly question, but was this tested on a mac? I found this 5 min after I started to use this. (started a new application to see if it was a bug in just the existing one, but have same error in both!)