Starting with Update 3 RC 2 (did not happen in RC 1), have VS 2012 pinned to the taskbar. Right-click the icon to use the "jump-list" and select a project to open with Visual Studio. While VS is loading it will show the "error list" window even if this window was not previously showing when you closed VS. Also, while the error list is showing, VS won't repaint that area, so the Windows desktop shows through. When VS has loaded the project, it will close the error list window.
This is a new bug introduced in Update 3 RC 2.