The Ctrl+click selection no longer works for overlapping entities?
Since AutoCAD version 2007, you can select from the overlapping objects with the new key combination Shift+spacebar (or from sub-objects with Ctrl+spacebar). The Ctrl-mouseclick combination is now reserved for sub-object selection on 3D objects (face, edge, vertex).
On the Select objects prompt, move your cursor over a crowded area with object lines/geometry a repeatedly press Shift+Space to highlight/select the desired entity.
If you prefer the old (legacy) method, you can switch the LEGACYCTRLPICK variable to 1 and AutoCAD will behave as in the older versions.
See the tip 8137 for higher AutoCAD versions.