How to edit array source object due to locked layer - AutoCad Civil

When editing the layer of an arrays source object the following warning message is displayed.  

 

Properties - Objects on Locked Layers
One or more selected objects is on a locked layer and cannot be updated.
Number of objects removed from selection set: 1

Causes:

This occurs if the arrayed objects and the source object are currently selected when attempting to edit the layer. 

 

 

Solution:

Press the Esc key to deselect the arrayed objects and then select only the source object.