Weird Unexpected Mirror Effect

Any ideas why a Windows build (made on a Mac) has a vertical mirroring effect when played?

No mirror shaders are applied to the camera— this was a total surprise. Camera settings attached— Clear Flags are purposely set to “Depth Only”.

Here’s what I did: I built an x86 .exe in Unity Pro 4.3.1f1 using a Mac.
Here’s what happens: When I run the game on a PC, the screen is mirrored vertically (meaning the bottom half of the display is the mirror image of the top half of the display. This doesn’t happen when I build a Mac .app

Camera Settings:

If you remove motion blur, any difference?

Yes, a difference indeed: that fixed it!
Huh, i guess Motion Blur has cross-platform issues…
Thanks, mgear!