Rollover highlighting and selection of 3D objects in AutoCAD 2011 is not affecting subobjects or the hidden faces of 3D objects like it did in AutoCAD 2010.
AutoCAD 2011 introduced the CULLINGOBJ system variable that controls whether 3D subobjects that are hidden from view can be highlighted or selected.
CULLINGOBJSELECTION is another new variable that controls whether 3D objects that are hidden from view can be highlighted or selected. This makes life easier working on complex 3D models.
Knowledge Base document: Unable to highlight or select 3D subobjects in AutoCAD 2011