ArenMook, I am sorry but your suggestion this time doesn't works.

I know that in Unity3D things don't change magically, therefore I have changed BoxCollider values manually... with my fingers!

Now, I have update NGUI version (thanks for this update!) and I have tried as you suggest and using "NGUI->Attach a Collider": yes now collider gizmo appear correct but after this D&D doesen't works.
In addition, if I place in a correct position the "DragDropContainer" BoxCollider, if I click on new "UITable" parameter "Direction" the collider is placed in a wrong place.
Please, just to be sure that don't exist any problem, can you try to convert "Anchor - Bottom" panel into a right anchored drag&drop panel and write here step by step what I must do to obtain this result? (Of course starting from Example 11-Drag&Drop)
In this way we can double check if all gizmos are correctly drawen.
Thanks in advance,
Kenshin
UPDATE:
Just for your information I have tried to add a new vertical-left panel to "Example 11" but starting from the scratch.
I have recreated exactly the structure that you propose for bottom panel, but I still have problems with collider and item position.
Please, check the attatched image.