Matheus,

If you have selected an object with the left mouse button and are moving it by dragging with the left mouse button you should not be getting a second copy. If you use the right mouse button then it will make a copy.

I have used a tablet with my computer and had a similar problem and found that my mouse button was being pressed by an object on the desk. Once I cleared the mouse button, the tablet worked fine and no additional copies were made.

Hope this helps.
Ray