Allah has not allowed that non-Mahram men and women freely associate with one another. No, they cannot. No where in the Islamic history has it been seen that a male and a female are friends. whether it causes problems or not, its not allowed. I can't understand that when the world is full of males as well as females why not girls find girl. Because they cannot control thier emotions most of the times.
Friendship can turn to special feelings and desire which can be disastrous if both are married.
I would not like to have my wife to have any male friend except the person I could trust. It is like the oil next to the fire. No it causes problems and the religion is against that if you believe in Islam. We are humans and satan is always with us. Even if we try to be friends with satan's existance, dont tell me you are perfect not to feel towards the other sex.