[ubuntu] Crazy pixellated desktop

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http://ubuntuforums.org – Hi all, For some reason, my desktop wallpaper appears really pixellated after loading a new workspace, opening an app, and after doing most things, which can only be fixed by reloading the wallpaper. My pc boots up with it looking normal, then either pixellates when If I look at new workspaces (e.g. hovering over windows which makes the background shaded) or at the desktop itself with nothing open, but never happens on both occasions. There's nothing technically wrong it's just really annoying. I've attached a screenshot of the pixellated background. Anyone know what's wrong, or how to fix? (Hardware)