I'm having the same problem. The last time I tried to add items to customize the toolbar, not only wouldn't anything drag at all (can't click on and move the items that should be movable onto the toolbar when in customization mode), one item actually disappeared on its own. Now I have only: inspector, library, and fonts on the right side. I have 6 files open right now and they all have different toolbars (see image). Please help! Thanks.