Probably I've a similar problem.
After the latest update (I updated on 29 Oct) the Unity 3D desktop background is black.
If a window was opened, then closed or minimized the picture of the window remains as background (little bit confusing).
Unity 2D works fine.
I use 64 bit Ubuntu 12.04.
If this is a different issue, I can open a new report for that.
Probably I've a similar problem.
After the latest update (I updated on 29 Oct) the Unity 3D desktop background is black.
If a window was opened, then closed or minimized the picture of the window remains as background (little bit confusing).
Unity 2D works fine.
I use 64 bit Ubuntu 12.04.
If this is a different issue, I can open a new report for that.