I'm experiencing this strange bug. Basically, if I enable the workspaces in Ubuntu 13.04 I see them, and I can go into different workspace by pressing Super+S and double clicking on them, but I am somehow inhibited to navigate into them with the keyboard (the typical Ctrl+Alt+Arrow). More strangely, this happens only for vertical workspaces, and I'm still able to navigate into horizontal workspaces. Obviously, I'm not experiencing this on my other 12.04 partition, so it's definitely not an hardware failure of some sort. Any help?