Since I updated my OS X to 10.9 Mavericks, I can't use any longer my Graphic Tablet, and I can't draw anything unless I get a new one.
It seems that the software my tablet uses is PowerPC. I'm not quite sure what that is, but I figured that the newer versions of Mac, since Lion, are not compatible with PowerPC and I can't use any application with this class (btw, my OS was a Snow Leopard).
So, I guess I won't be uploading new drawing until I get a newer graphic tablet, and obviously make sure it works.