Looks like KB2670838 might be a bit of a pain.  It seems to be messing with some systems, including causing a strange colour change in Revit 2012 as per Color Change in Revit 2012 after Updating Windows 7 – The Revit Clinic

The update seems to be related DirectX, including Direct3D.  You can read more about it at:
A platform update is available for Windows 7 SP1 and Windows Server 2008 R2 SP1

Windows Update sometimes becomes quite an annoyance doesn’t it?  I previously posted about problems with WDDM1.1 and Graphics Adapter WDDM1.2.