Cannot Edit a Block Diagram from a VI

Issue Details

I have opened a VI from the LabVIEW examples or from another external source.  I am unable to move, select or edit any of the components from the either the front panel or the block diagram.
Is there any configuration for locking a LabVIEW VI? 

Solution

There are two different configurations that can cause this to happen:

1. The VI is in run mode: The VI can be on either edit or run mode. To change this configuration you can just go to VI toolbar a select Operate>>Change to Edit Mode (or press CTRL-M)
2. The VI is locked: The VI can be locked with no password from the VI properties. To disable this feature just go to the toolbar menu click on File>>VI properties from the dropdown menu Category select Protection, and change from locked to Unlocked. This can be reviewed in the following image:

After changing this configuration you should be able to edit any component of the VI.

Additional Information

You can check here the difference between the edit mode and the run mode:

Edit Mode

Edit mode is the primary design-time mode from a VI.  From Edit Mode the user can construct the Front Panel.  User can set properties of the controls from control specific selection adorners, the contextual ribbon tabs for the control or from the properties tool window of the editor. 
Users cannot directly interact with the controls themselves.  There is no direct manipulation of the controls available when the VI is in edit mode.  When in edit mode controls do not react to user input and do not transition between visual states.  Also, user defined animations for the panel do not run.

Run Mode

When a VI is in Run Mode its front panel cannot be edited.   Only direct manipulation of controls is available.  Controls can no longer be selected.  There are no selection adorners available, contextual tabs are not shown for controls, and the properties tool window does not allow editing of the properties of the panel or controls.  The primary way to enter Run Mode is to run the VI.  When a VI is running it is always in Run Mode and the user cannot transition to Edit Mode.  Users can also switch to Run Mode before running the VI by selecting Run Mode from the Front Panel ribbon tab that is displayed when the Front Panel Editor is active.                  
Switching to Run Mode explicitly is considered an advanced use case and most users will not do this.