ok i bet i know what's wrong, but not why it's occured for you
i'll bet somehow it's "docking view" has gotten messed up and it's just that all the docked windows are "closed"
maybe the docking preset files got messed up, or something like that.
The same thing would happen if you somehow dragged all your docking windows off the main form and then closed them.
Try choosing another docking preset from the "Presets" menu. You should see views for "Standard" and others to choose from, if not then your installation is missing these and that would explain the problem, and you should reinstall.