PM 4.6 on a Mac Pro OS X 10.5.6...
In the Preview display if the toolbar items are set to "Text Only" via the context menu, all the items are grayed-out and most are disabled. But if you click on "Single preview", "Portraits" or "Landscapes" the toolbar then reverts to the "Icon & Text" setting.
This behavior is also present in Ver 4.5.4.