I'm not exactly sure what this empty box on my desktop is however it's been there pretty much from the beginning. I'm running Kubuntu 12.04.
The empty box wasn't an issue until I put a new wallpaper on my desktop (with the Scaled & Cropped setting), and it's being pushed to the right. Not that it should matter, but the box and wallpaper are on my 2nd monitor.
I thought it was a widget, although I'm not sure now. I unlocked widgets, then right-clicked on it. It always displays the same menu as right-clicking on the desktop anywhere. My understanding is that widgets will display a different menu.
I have also looked at Desktop Effects and they aren't on, so that's probably not it.
Desktop effects are not available on this system due to the following technical issues: Required X extensions (XComposite and XDamage) are not available.
Any idea what this may be and how I can remove it?