I could understand the feeling of having it hard to be friends with girls, and yes, I think it has something to do with not being able to know how to carry or settle yourself being friends with another girl. At least that's how it is for me. Men on the other hand, are easy go lucky, most of the time, and flirting apart, it's easy to position yourself as friends with a guy, cos mostly you can share what they find hard to figure out, women's emotions. When they have girl troubles, you can easily give them advice, compared to giving a girl having guy troubles advice, if that make sense. I guess there's just the mystery of a woman and a man's chemistry, even purely platonic.
Nevertheless, I don't believe that it's cos girls are whiny, annoying, girly girly bitches with all the worse derogatory names you can call a girl. Even the most boyish girl has her girly side. Even lesbians. We can't deny that biologically, we are women and that our emotions are more inclined to the feelings women often feel. Even if we don't speak of it or share a type of friendship that we like, we'll always be able to relate to the same feelings we generally go through, as women.
Most of my friends are girls or gays or lesbians and we don't go shopping and do girly stuff. We're the most plain looking bunch you could ever see of a group. We don't usually talk about how we were flirting with this guy and how we hate this girl, but we just talk about stuff we share in common like movies, songs, food, or life in general. I could also do that to a guy friend that I have. I don't know how to explain it, but when you're really friends with someone, you don't always think what age/gender/orientation/faith that person belongs to and I find that really amazing. To share a relationship that's purely friendship.
I don't think it's a problem to have more guy friends just as long as you also give girls a chance to be your friend and get to know them beyond the girly exterior they may have and learn how to deal with the intimidating feeling you have with them. After all, when you get those heavy days, a girl friend will be the one to lend you her extra pad (hehe)