What if you right click on the workspaces in the lower right, remove that from panel, right click on the panel and hit "add to panel" and re-add that section. Maybe it's a bug with that particular instance of workspaces you're looking at. Once or twice in my 4 years of using Ubuntu I had that with my trash can, where it acted weird or wouldn't open. When I readded it, it was fine.
Give it a shot, let us know if that helps any.