Graphics glitch in driving tutorial?

New to Unity, and working my way through the tutorials and getting up to speed. So far, everything is good except for a persistent graphical glitch in the driving game tutorial that I'd really like to get sorted.

I downloaded April's driving tutorial from here. Unpacked it and opened up Assets/Scenes/TheTrack.unity. In the editor, I am seeing a copy of the terrain rendered upside down in the lower left quadrant of the window, over the top of the scene graphics. See screenshots here and here. In game mode (when I play the scene) everything looks fine. The trouble is only in the editor.

It looks like Unity is rendering to a texture, but not erasing or overdrawing it when it draws the scene. I'm running on a 2009 unibody MacBook Pro (model ident MacBookPro5,3), so pretty common hardware. 2.8GHz Core2 Duo, 4GB. I get the same issue with both the 9400M and 9600M GT video.

I logged an issue for this back in May, but have gotten no response so far. Hoping someone here can put me on the right track. Any ideas?

Just a thought, but that water doesn't look like its rendered using Unity Pro. At least I think from memory that the advanced water shader needs Pro featurs? In which case if you are using Indie version, perhaps its something to do with that shader? Maybe if you tried the Pro trial and its now switched to Indie that messed up the shader?

What happens if you hide the water in the scene? Do you still see the terrain? Is it definitely a render, not an actual mesh?