Thanks for replying. I tried what you suggested:

-deleted history before making the constraint;
-froze transformations;
-then created the hinge joint;
The pivots are in the centers of the rigid bodies.

The problem is that I can't control properly the green axis of the hinge constraint that is displayed, although I see that the constraint transformations seem ok in the attribute window... what does the green axis represent? because I see that it's not a representation of the constraint transforms. Sorry for the questions, I just started trying out things in Maya.