I have Large Assembly Mode and Large Design Mode disabled.   Nothing is loaded lightweight.  

When I hover over an assembly component (of a small assembly) in the feature tree, I get a bounding box-ish highlight and when I click on the component, the box disappears and the component is highlighted:

With a large assembly, I get the same highlight, but after I click the component, the component is highlighted as expected, but the bounding box thing doesn't go away:

If I select multiple components, I get a mess like this:

Does anyone know the cause and more importantly can it be eliminated?