3D object blocking all mouse clicks on 2D object in Unity 4.3 2D project

We're seeing an issue in Unity 4.3.0f4 build where if a 2D and 3D object are at the same position, but different Z axis position for example the 2D object is in front of the 3D object and each has their own respective 2D and 3D box colliders, the 3D object receives all the mouse clicks and the 2D object receives none.

If I move the 3D object to a different X Y position, then the 2D object receives the mouse clicks. I've tried putting the cube in front of and behind the 2D object with the Camera facing down the X Y plane and the Z positive axis going away from the camera, and the 3D object always receives the mouse click.

Has anyone experienced or knows about this issue?