Yes, I can confirm a similar problem is happening to me. I'm running windows 7 64-bit. 1900x1200. When I use the desktop switcher to pan over to another desktop using the left-right buttons, it switches to an older "Windows 7" wallpaper and when releasing it switches back. It seems the current wallpaper becomes semi-transparent and shows the older wallpaper image through. In this case the older wallpaper is bright blue so it really shows up.
I've found no way to trick windows into removing the older wallpaper.
