i've just lost a friend a.k.a. friendship between male and female

I was raised believing that friendships between boy and girl are just as unproblematic/problematic as friendships between girls, but as I grew older this picture has changed.
First I thought to my self that maybe it was an exception when a friendhsip between me and a boy failed but with time I realised that it is just not working. Maybe it is possible for other people to remain platonic friendships between sexes but for me it has never worked in the long run. Unfortunately!

Whenever a friendship with a boy fails, I promis myself to never befriend a man again, but im not successful at that either!
Having a western and very liberal background I believed that since we are all thinking and liberate human beings no harm can come from friendship, but life has proved me wrong so many times!

To get an insight on the islamic point of view check out this nice articles I've found:

Premarital Relationships — Why Not?
http://www.islamonline.net/servlet/Satellite?c=Article_C&pagename=Zone-English-Youth%2FYTELayout&cid=1162385898879