Why can't i add friends?

How come when I try to add people as friends it doesn't work?
Is there anyway to tell if I can add someone as a friend because whenever I try adding people my computer freezes up and I have to start the internet again?
-Any suggestions?

If you are over 18 and try to add an underage (less than 18) member as a friend, they have to *approve* your request by default, unless they change their profile to automatically accept all friend requests.

I have tried to add people over 18 too but my internet freezes up and I have to close it and start it up again. Is there anyway to know who I can add and who I can't add as a friend?