Among the private feuds going on during the minority of Duke William was one that erupted between William Talvas and William fitz Giroie. William fitz Giroie was a vassal of William Talvas and his father Giroie, Lord of Échauffour had assisted Talvas' father and uncle in the struggles against Herbert I Wake-dog, Count of Maine. William fitz Giroie himself had greatly assisted William Talvas in obtaining his own lands, apparently by force. But William fitz Giroie was also a vassal of Geoffrey de Mayenne, an adherent, in turn, of the Count of Maine. About 1044 William Talvas attacked the castle of Montaigu which was being defended by William fitz Giroie. Unable to defeat the castle William Talvas captured Geoffrey de Mayenne and held him prisoner until William Fitz Giroie destroyed the castle of Montaigu. William fitz Giroie immediately razed his own castle to free his lord and in return Geoffrey de Mayenne built fitz Giroie a new castle at St. Cenery on the river Sarthe. This apparently caused great resentment in William Talvas.