In the first group I gamed with, I was the only girl. The guys were totally cool and helped me learn the ropes. In fact guy was even more psyched than I since before I came along he had always lost the coin toss and ended up playing female characters.
Then, I started playing with my boyfriend's group that he DMed, and there was another girl who was engaged to one of the other players. So far, absolutely no gender-related problems within the group.
In fact the only thing about being a female gamer that bothers me is that, outside of our group, I know no other girl gamers. I tell my girl friends that I game and they treat me like I'm weird. At a previous job, I let slip that I gamed and one of the other gals thought it sounded neat but then one of the older women found out. She spread a rumor that I was actually a bruja--a witch. That makes for a really strange working environment.