These days i think it has less to do with gender, and more to do with opportunity. Traditionally, men had more opportunities for affairs as they were the ones in the workplace, and out in the world in general. Women traditionally stayed at home with the kids, keeping the home fires burning.
But today, more women than ever work outside the home and have the same opportunities for affairs that men have.
I think that given the right conditions, anybody has the potential to cheat.