This happened to me just now. I killed u2d-shell, because it was rendering wrong already: it left a white vertical column when hiding, obscuring the view to the app underneath. When it restarted, the launcher was only 7,5 icons high (looks like Lohith’s screenshot, though slightly higher). Neither of these symptoms have occurred prior to this.

A new `killall unity-2d-shell` fixed the issue for this session.