Today I will show how to fix your 3D Cursor using python script.
First you can select Screen layout : Scripting from top of the Blender 3D application.
Then on the bottom of this ( python console ) type this python script:
view3d.cursor_location = (0.0, 0.0, 0.0)
Now your 3D Cursor will be into origin of 3D view space.
This will be useful when you want to select many objects to same origin geometry.