So... none of the suggestions above worked for me, neither having a fresh install of SketchUp 8... So I determined that it must be something in the model itself.
A clean new project doesn't have the bug, only some files that I work on from the get go.
After cutting and pasting the elements of the file I was having an issue with, into a new SketchUp project, the issue isn't there anymore.
I have Layers Panel & Layer Manager, and they don't seem to be the problem (evident by the fact that the issue persisted with a clean SketchUp install