OP: http://web.roblox.com/Forum/ShowPost.aspx?PostID=120623356
The issue is that when you have a part with a SurfaceGui on it, and a transparent part (of ANY transparency other than 0) in the way, blocking your view, the SurfaceGui is shown with no dimming. e.g. looking at it through a 0.01 transparency part produces the same effect as a 1 transparency part.
Which should not happen, clearly.
Screenshot 1: http://puu.sh/5SHft.jpg
Screenshot 2: http://puu.sh/5SHgp.jpg (0 transparency)
Screenshot 3: http://puu.sh/5SHhy.jpg (0.001 transparency)