It may be that maggie is not as dominant as the dane....they can be dom-aggressive as a breed sometimes I think...The only thing I would suggest is exercise the dane until he is too tired to move, and then train him in manners and in the family rankings. Ever watch Cesar Milan's show? Some of that stuff really works....the dane needs to know he is not in charge and that on the food chain maggie is a wee bit higher up....teach him some manners and things might improve....just a suggestion.