I don't know what I did exactly, but when my touchpad "froze" (another story) I started to make random combinations with the keyboard, and seems that accidentally I deleted my workspaces. I had 4, and now I only have 1. It's curious, but on Unity-3D, the 4 workspaces still there (cause it's use compiz, no?).
Well, how can I restore my workspaces?
Edit: Ok, tried to do what says in this thread How to add multiple workspaces in Unity 2D? but don't work for me :(
On the dconf editor, in the /apps section, it doesn't shown /metacity, but I have it installed!