With at least one open window when mouse hovers over "Show Desktop" icon , the revealeddesktop has opaque white bands streaking vertically over the wallpaper.This resolves upon clicking the icon. Don't think it was like that before, perhaps I didn't notice it.

If you simply hover on Show Desktop button....it shows all active Apps Window transparent w/ border....beside it by clicking on Show desktop button....it minimize all active window to Taskbar.- Ramesh Kumar